@Beemer 

Did you remove Adobe Flash from your PC recently?  Never seen the picture you ahve posted but it looks like its looking for Flash installed.

I know flash was made end of life a few days ago (12th I believe) and most windows PCs are removing this automatically now as its classifed as "risky".   

See if there is an update non flash version of the App for you, if not you might want to install flash temporarily to get this working.

Hope that helps

@Philbert  Thanks

I've seen this in other posts too. Sounds like it is Flash.

Will check on TP Link to see whether they have a new version

@Beemer 

@Fae 

 Hey Fae.  Do you know if this has been addressed in a new version of the TP App without Flash?

@TP-Link Thanks for your very quick response.

I'll try the software link.

I've had the kit for some time. I had lots of problems with it when I first set it up - in addition to the kit, I also have other, older adapters, so it's a bit of a mixed bag.

I eventually got things working (updating firmware, moving adapters about, etc.) but it's never been truly stable and we often have to switch the adapters off off and switch back on again or (rarely) repair everything.

I've sort of got used to this and it seems to have stabilised over the past couple of days.

I know it can be a variety of things - extenders, firmware, electric circuits in house, fuseboard, etc.

Trouble is, it took me so long to get things working originally that I don't want to go through it all again - it is time-consuming and, if I'm honest, stressful (paying lots of money and not getting results you expect).

I'll look at the lower VDSL mode and see how it works, but don't worry too much about this.

Thanks again for your help.

@TP-Link 

The utility works - sort of!

I changed to the lower VDSL mode. It reduced transfer rate between the master and one of the adapters from 600+ mbps to 230 mbps. I tried to change it back. It says it has saved the setting but the transfer rate does not improve. After closing the advanced settings and reopening them, the lower VDSL mode has reverted to selected, so now I have an adapter with lower VDSL mode that I don't want.

@Beemer 

Temporally change your PC / notebook date time to earlier than 12 Jan 2021 (Adobe Flash EOLS date). Once tpPLC utility is launched, you may change back the date time to current. This workaround works for me. Cheers...

@Beemer 

I have had the same issues using Powerline adaptors TL-PA8030p 2.0 and TL-PA8010P 2.0 all at latest firmware levels.

I noticed no real difference in performance with the Lower PLC-to-VDSL Interference Mode" option enabled so wanted to return it to disabled.  The system says "Saved" but on rechecking the setting it is still enabled.

In the end, the method I used to disable the option was to perform a hard reset of all devices and then to re-pair them all.  Not an elegant or quick solution but at least it worked.

@Beemer changing dates is a workaround, but I cannot believe that TP Link as a network company is not able to fix this utility, this is software not rocket science, so please TP-Link fix this tool, We cannot all throw away our powerline devices because of a non-functional tool.