Unable to connect Chamberlain garage door opener via 5g internet

My original gateway worked well with the Chamberlain door and MyQ app. It was when the T-Mobile gateway was replaced due to its buffering and freezing issues that it no longer connected. T-Mobile claims nothing changed between the gateways. Replacement was a refurbished unit, the same model.

This is an update to my original post. 

Having the same issue. Both of my Chamberlain garage openers worked fine up till 36-48 hours ago and then became unreachable in the MyQ app.

I figured TMobile changed something, like a blocked port (i.e. 8883). 

To test this, I reconfigured the Garage openers to use my Verizon Hotspot and everything worked fine.

Looks like Tmobile added some filtering.

Please fix this or give us the ability allow exceptions on the router.

I have spent hours on multiple calls to both T-Mobile and Chamberlain. Each points the finger at the other. No resolution yet! So frustrating to have a smart garage door opener that is not. 

IMO, the change has to come from Chamberlain to have the MyQ server listen to open ports.  They will claim they use this port for security purposes.  Hardwired connections like ATT might be secure enough to have the port open, not so much with 5G internet using the cellular network.  I doubt T-Mobile will open the port (8883).  

The more complaints Chamberlain gets, the more likely they might take action.  Open a ticket with them.  I pointed out to the Chamberlain support tech that this issue will only grow in frequency and just marking it as a known issue wont make it go away.