X750ca connection issues on T-Mobile

Hoagie · 2020-11-13T16:15:29.364Z

I’m having issues connecting my X750 to T-Mobile.
I can register the sim in default LTE mode but have essentially no data passing. Previously (last month) I found that if I set the AT+QCFG to 3,1 (WCDMA only) I could connect and get resonnable data throughput.
When I change the QCFG to WCDMA only I now get “Sim card not registered message”. Can someone please provide me assistance or let me know how to contact GL-inet Support for assistance.

alzhao · 2020-11-16T07:50:42.324Z

Can you try AT command AT+QPRTPARA=3 to reset the modem?

Hoagie · 2020-11-20T16:47:47.571Z

I spent most of the yesterday working on this. The +QPRTPARA=3 did reset to LTE connection but speed was only 0.02 Mbps upload and download. Modified the configuration to 3G (WCDMA) only and made connection with reasonable throughput but the connection locked approximately a half an hour after.
It appears that the connection was using an AT&T feed on Band 5. When restricting connection to Bands 2 and 4 only I connected to T-Mobile’s Band 2 and was able to download data for a short while even though the UI showed the “Sim not registered” message. I should note I have a very weak signal power (-115) at the house.

Doing more research online I came across some forum posts describing problem with at least some EC25AF modems locking up due to minor power variation during bootup. See links:
https://forums.quectel.com/t/quectel-ec25-mini-pcie-sim-detection-problem/5293
https://forums.quectel.com/t/quectel-ec25-mini-pcie-usim-detection-problem-usim-vdd-0v/3086

Can anyone provide more feedback?