@David-TP 

Hi there,

it's Frank from Frankfurt, Germany, here. I own a M8550 since early August, it replaces a Netgear M1 in my camper.

I came across a compatibility issue with some SIM cards from the German provider O2 - I try to explain all the details that I found so far. The router is running on firmware Build 250704 which should be the latest one AFAIK.

I have a plan with O2 that allows me to use multiple SIM cards: so called multi cards for voice and data, plus cards for data only. All cards as well as my plan are enabled for 5G SA by now. In the following I'll talk about "old" cards, which refers to cards issued about 2 years ago, and "new" cards, issued since August 2025.

The M8550 works fine with an old as well with a new multi card (voice/data 5G SA) and with an old data card (5G NSA, meanwhile replaced with a new SA-enabled card).

However, it doesn't run stable with new data cards - I've tested this with two different cards. The following issues occur:

After booting, it takes long until a 5G connection is established. In the meantime, all bars are gray. In the Tether app the router gives the message "No network found. Move to an area with network coverage". After a while, I might get 3 of 4 bars and can use the connection, but after a while (from 5 to 50 minutes), data can't be transferred any longer, although it still displays 3 of 4 bards. Later all the bars are gray again, but it doesn't fall back to 4G. After some time there is a connection again, but it all starts again from the beginning.

The same new data cards work fine in two other routers, allthough these are 4G only.

When the M8550 is set to "4G only" mode, all cards run without problems, even the new ones.

For now, I'm using the M8550 with the multi card (voice/data). However, this is just a workaround, since in some EU countries it's not possible to use two cards with the same voice phone number simultaneously, so I need to be able to use data cards in the long term.

Let me know if I can do anything to help diagnosing the issue.

Regards
Frank

  @David-TP 

Is the Professional R&D team planning to solve the problems mentioned before Christmas? For over a month now, the display can no longer be completely deactivated, as the backlight is always on and the battery can only be charged to 100% when the ambient temperature is below approx. 20° C (presumably due to overheating problems almost always only to 80%)

  @David-TP 

Actually, I discovered the Log option in the Web UI yesterday after posting my issue and already created a log using Debug level. I also created screen shots. Meanwhile I got a support ticket and will answer these questions by e-mail, as requested from support.

Regards,

Frank

  @David-TP 

Does the optimized temperature control go hand in hand with a loss of reception for mobile communications and a loss of transmission for WiFi or what are you optimizing via software? I'm starting to think that the hardware is the reason why the device gets hot quickly and without any load.