@Kevin_Z 

Hey, thanks for replying.

Here there are 2 shots of the router config, and one of the iOS "Remote App" (Pioneers').

  @betauser 

I suspect the problem is you have Access Authentication on.

I had to remove that at as my iOS and Smart TV apps can't handle the request for a P/W and report no access.

Windows apps can handle that and will pass on your password if the same as the Windows User.

  @betauser 

How many media files and how many total files do you have present on the USB HDD?  I suspect this is NOT an actual access issue as DLNA has no security constraints.  In other words, the username and password configurations should be irrelevant.  (They would only apply for SMB access as with windows or mac file browsing.)

More likely, the root cause of the issue is a limitation of the DLNA server TP link provides on the AX50 (and other SOHO routers).  These have been known to have a limit to how many files they can support.  When that limit is exceeded, the DLNA service may stop functioning correctly.  This will suddenly prevent media player devices such as the Pioneer HM76 from being able to access the media files on the USB drive connected to the router.  But other, non-DLNA devices such as PCs/Macs/mobile devices will still be able to connect fine for general purpose file access.  Have you recently added more files to the USB drive in question?  Can you try temporarily removing some portion of files and re-testing?  Note that even non-media files count towards the DLNA server file limits.  So adding non-music files to the USB drive very well could have caused the limit to become exceeded and caused the DLNA service to stop working.

Hope this helps.

  @IrvSp there's no Windows involved. I tried both Access Authentication ON and OFF - no difference.

  @MikeS21 Hey, thanks so much for the detailed reply.

I've done this before, and tried it again - I stuck a small 64 GB USB with music only, shared it on the router.

And again - the same message appears.

betauser wrote

  @MikeS21 Hey, thanks so much for the detailed reply.

 

I've done this before, and tried it again - I stuck a small 64 GB USB with music only, shared it on the router.

And again - the same message appears.

 

betauser wrote

But all the contents of my HDD / music is visible and playable via another Pioneer app - MusicControl. Which is though not good at all, and even the playback is OK in general, gets interrupted by phonecalls (WTF) and also you loose control over the iPhone volume control.

@betauser 

The issue I believe you're facing isn't a matter of having music only files versus music and other types of files.  It's a matter of how many files (regardless of type) are on the storage device and possibly how the files are organized, e.g. several small folders vs one or a few very large folder(s).  I honestly have no idea what the actual limit may be in this case but this type of issue is very common with the DLNA servers built into consumer routers.  These "mini" DLNA servers don't tend to be very robust and are prone to stop working for seemingly no reason.  However, oftentimes, the failures are due to some undisclosed file limit being exceeded (too many total files on the drive or too many files in one or more folders, etc).  When this happens, DLNA type connections will suddenly stop working, but other types of connections will continue to work fine.

To clarify, DLNA service is a form of media streaming (photos, audio, video) which has no security, is "stateless" (relies on UDP data transfer).  This allows it to be very lightweight and resilient against intermittent network issues.  The data being streamed from the DLNA server to the DLNA clients can tolerate minor disruptions without affecting the user playback experience.  It's for this reason that media devices (TVs, audio receivers, multimedia centers, etc) are built to support the DLNA standard.

In contrast, generalized file sharing protocols such as SMB are stateful and require much higher overhead.  SMB is the service which allows any files on your shared drive (music or otherwise) to be accessed from other devices which have SMB compatibility and appropriate access permissions.  The main purpose of SMB is general-purpose file sharing (originally for network computing), but this allows it to also be used to share media files.  However, when doing so, the connection will be more susceptible to network disruptions and can even suffer complete connection loss.  Even without network congestion, SMB playback requires greater resource demands on the client device (as the media file must be loaded into memory rather than streamed in real-time) and can suffer disruptions from other background activity (e.g. phone calls).  My assumption is your other "Pioneer app - MusicControl" playback supports the SMB protocol and is what allows you to still be able to playback your music.  But as you noted, it's not as fault tolerant and it doesn't support features that are specific to media playing (e.g. volume control adjustments, etc).

The bottom line is I'm convinced that your SMB file sharing is working fine but your DLNA service has stopped working.  In order to address the DLNA issue, my only suggestion is to try restarting your router and incrementally testing DLNA playback with a small starting collection of audio files and then incrementally larger collections of music.  

Admittedly, it would be ideal if the DLNA service did not have any file count (or other undisclosed) limitations.  But in all honesty, this type of issue plagues all consumer router brands (e.g. Netgear, Linksys, etc.) as these features are somewhat "tacked on" more for marketing purposes than for extensive use.  So you may also want to consider investing in a more robust solution for your DLNA library (i.e. NAS).  

  @betauser 

For additional reference, I found an old forum topic which states there is/was a 10K file limit for Archer C59 routers.

Media Share File Limit? - Home Network Community (tp-link.com)

It's not clear, however, if that limitation still applies to the C59, whether it applies to the AX50, and/or if it will manifest problems in the same way.  For the C59 limitation, the DLNA service would still work but not all files would be accessible.  In your case, the DLNA service has stopped working entirely.

Regardless, I'm still convinced that you're facing a DLNA issue and that it's highly likely it's related to the quantity of files on your drive.  Another test you try to perform is checking with other DLNA players (VLC media player is a free app available on almost every platform) to confirm whether any DLNA access is available through other clients (i.e. rule out that the issue is specific to your Pioneer devices).

  @MikeS21 thanks, just tested with VLC on iOS - shows a small part of the music (folder, files, etc.) on my drive.

Same happens if I try to reach that same shared HDD with a Win 10 machine PC on the same network.

Same goes for the (not really usable) Pioneer Control app... displaying just a few, contrary to all contents a couple of days ago.

Still, the Pioneer Remote App displays the same message: Access denied by server.

Conclusion: not tonly does the Pioneer Remote continue not reaching my media server, but the rest of the devices started displaying a small part of its contents.