I'm not technical, but here's what happened to me.
I have a contract SIM with EE, about 3 months ago I brought the Archer MR200 and installed an outside aerial. Took out a shared SIM on my main contract.
Put Sim in router and was enjoying speeds of 70mbs, on a Wednesday about 3 weeks ago it suddenly stopped working. The SIM was giving off a 4g signal but no internet.
When I put my main SIM in the router it worked and vice versa when I put my shared SIM in my phone this too worked.
Called EE they couldn't detect any problem and suggested a new SIM, I went to EE Shop and took another SIM, this still didn't work.
Contacted EE again and they couldn't understand the problem, they raised the fault to level 2.
Level 2 downloaded the router software from TP and were able to relplicate the problem.
After about 4 days they resolved the issue, the router was not the problem according to EE.
The problem, explained to me was something to do with certain Data SIMS and IPV6 upgrade.
They had quite a few complaints about the same router which had stopped working and decided to issue support, even tthough the router was not EE.
I'm happy to give my mobile number on Private Message and you can call EE and explain that you have the same problem as me, they will find the ticket linked to my number and hopefully resolve for you.