SIP Alg on Tmobile home Internet

That is precisely my situation as well. I also have the KDV-21 gateway and a VOIP office phone that worked fine until it didn't one day. How exactly does one reset the digital phone module? ¡Gracias!

My digital phone would not call out or receive calls but I had a dial tone. 

I called my phone service provider and they said that I needed to disable my Sip and ALG. They said I would have to call my network provider to get them to do this. T-Mobile said that the network box that the KVD21 box do not have access to perform those functions. Their box is a simple set up with no configuration capabilities.

However I solved the problem by resetting my digital phone module and unplugging all cables and power connections from the router and phone module and then reconnecting them.

I can now receive and dial out.

Not easily. If you have the Arcadyan KVD21 5G gateway, you have almost no access to it. DHCP, NAT, etc. are not configurable on the gateway.

For more flexibility, check out Nater Tater on YouTube for some workarounds, but be prepared for some work on your part.