Mystery of disappearing 5G connectopy for 5G business internet

Hello everyone,

TLDR: I had my 5G business internet went to 4G/LTE only and can't make it back to 5G. Anyone has seen similar situation?

TLDR: I had my 5G business internet connectivity going from 5G to 4G/LTE only and can’t make it back to 5G.

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I subscribed to 5G business internet with static IP once it become available in our area in January. In Feb I received FX3100 gateway, provisioned it, was getting solid 4 bars in the information page. I switch it to pass-thru mode, to use my router as wifi and gateway and everything was fine - getting 130mbit download and about 20mbit upload.

Couple of weeks later I say that speeds have dropped to 4G only. Rebooting the router, resetting to factory settings did not help. I called support and they shipped replacement gateway.

Replacement gateway came with its own SIM card. When I turned it on, it booed and came up with solid 5G connectivity - blue LED on and 4 bars from 5 in the information display. Then I put my old SIm from previous router) in new and power cycled it. It came back - with 4G connectivity only.

I put new SIM card back, power cycled and it came back again with solid 5G. However this new SIM card had no internet connectivity, despite that cellular 5g connectivity was on. 

So I called tech support and the first level could not do anything. They transferred to the second level and after 15 min of provisioning new SIM card (that came with the router), updating profiles, etc, etc. They asked me to unplug power, wait 2 min, plug it back.

I did and router came back with my old static IP and… with 4G connectivity again. Remember, when SIM was unpovisioned - it was showing 5G fine.

I am telling all this to the support and they are telling me - weeel, there might be 5G connectivity problem in  your area. But when I asked how it was that with unprovisioned SIM I was getting 5G - they have no answer.

No they are telling me that they will check something on their side and call me back.

So…. anyone have been in the similar situation? How it can be resolved?