After considerable time lost trying to figure out why I was not able to get remote access over public IP, I ended up going with static IP address. Once the IP was assigned to my account, I was able to successfully SSH,HTTPS and connect to a VNC server running on host behind firewall. This lasted about 5 minutes and then I lost all access to connect remotely. Restarted multiple times and device LTE pulled the correctly assigned static IP but could not access remotely. Another Call to LTE provider and they determined the APN was incorrect and had me assign a different APN for static configuration and after doing so, I was able to again regain remote access for about 5 min and several restarts. After that, I was again unable to connect remotely. After several more calls to LTE provider and them switching me over to a different class of static IP, I have yet been able to regain remote access. Note sure if they even have a clue as it seems like I talked to 6 or more teams. It just seems like there is a traffic rule being hit on their side that is dropping incoming requests.
This seems more of a provider issue blocking incoming requests than a device issue but wanted to ask the question anyways to see if I am overlooking anything. Not sure why it worked the first several times after assigning static IP and then second time updating APN#. This has been escalated to more advanced backline team but since they show this as unsupported type, not sure they will engage. The device works fine on their network for all outbound traffic and does what it is supposed to but I need some port forwarding for failover and since I cant establish inbound connections, this does me no good. I am going to try another provider SIM and see if I get the same results. Wanted to see if I am overlooking something on the device side that may be causing this issue.