Hi…
Here… The C50 only do Internet, through LTE 5G. I am using it at my workspace… and this the only internet I have, here.
Hello,
I hope you are doing well.
Our R&D team has developed a beta version of the modem firmware, and we are currently looking for users who are still experiencing this issue to test the firmware and verify whether it resolves the problem.
If you are willing to participate, we can arrange a remote session with our R&D team to install the firmware and investigate the issue further.
Please let me know if you would be available for such a session.
Kind regards,
V.
Was there any volunteer who tested the beta modem firmware already ?
Best,
Christian
For your information…
the problem seems to be location-dependent.
I was traveling with the router for two weeks (Germany, Austria etc.) and had no 5G problems. Now I’m back… and the problems at this location/cell tower are back. 
Hello,
I am still arranging remote sessions with the users, if you would like to participate, please let me know.
Kind regards,
V.
Hi, same issue here.
Hello,
For troubleshooting purposes, we will require more sensitive information from your end, such as the troubleshoot file, which may contain passwords, public IP addresses, serial numbers, and such. To avoid leaking this information, we have sent you a form to fill out, which you will receive in your e-mail inbox that you have registered your account with in the forums. In the Ticket ID field of the form, please enter the ID of this thread, which is 18440-4.
Please let me know once you filled out the form.
Thank you,
V.
I am available this week and we can schedule a remote session for troubleshooting and beta modem firmware tests.
Best,
Christian
This update fixed the problem for me for about two weeks, but as of today the 5G problem has returned. No other changes to the system.
I found this thread searching for “5GMM reject cause: N1 mode not allowed”.
We have a RUTM30 on O2 network in Northern Ireland giving the same error and the same problems the modem endlessly resetting. In 4g mode the unit operates ok but it can be a struggle to get it to switch back.
Unit: RUTM30
Modem Firmware: RG520NEBDCR03A05M4G
System Firmware: RUTM_R_00.07.22.1
Installed 31st of March 2026.
Hello,
Thank you all for your patience. We understand that this issue has caused an inconvenience.
After a detailed analysis, our R&D team has prepared a new firmware release for the RG520NE modem, which should become available on the DFOTA server within the next 24-48 hours.
We recommend updating the modem firmware once the notification appears in the WebUI, or manually by navigating to System → Firmware → Update Firmware.
Kind regards,
Matas
Hello,
We want to sincerely apologize for the experience you’ve had with your device and for the delays in getting back to you.
With the help of the information provided on our forum, our R&D team analyzed the situation and identified the issue, which was escalated to the modem manufacturer with critical priority. Now we’ve received a new firmware, which passed internal tests, so please test whenever possible.
If you are currently on modem firmware A05 (also soon there will be updates from older versions to newest A06 version as well - keep an eye on it), please update using the WebUI DFOTA method:
1. Navigate to System → Firmware → Update Firmware → Modem update.
2. Proceed with the update from the server.
You should be able to run on 5G again without the instability after this is applied.
If you encounter any issues after applying the update, please reply here and we’ll ensure it receives prompt attention.
Thank you for sticking with us this long, and we hope this puts things right.
Best regards,
Hello,
I have updated to RG520NEBDCR03A06M4G this morning and changed the network connection type to 5G. My first tests are looking pretty good. It seems to me that the issue is fixed (hopefully). I will continue testing and I will report any issues back.
Teltonika ! Please keep in mind and forward this to your management !
We decided to pay for world class industry router and we expect that you continue to deliver high class products and services. Testing and quality control is essential to your products and brand.
Best,
Christian
Hello,
I’ve also found this topic while searching for “URC Event: 5GMM reject cause => N1 mode not allowed”.
I have the issue on two RUTM30 devices for months now (see my topic here: RUTM30: cannot get IP connection (PAP authentication)).
In my case, the following does not fix the issue (I can’t get any data connection):
- setting “Preferred network type” to “4G only” or “4G/3G auto”
- using the modem firmware RG520NEBDCR03A06M4G
(I’m already in contact with the support, I’m not hijacking this thread, only adding myself to the list of impacted users)
With the new update, the issue is solved for me!
Thanks for the support! 