Tower Locking

Can someone elaborate how to set this up? I see a list of towers when I let it search. But when I lock one with the right prefix for tmobile, then I cant connect. Says some kind of sim error. Sometimes it shows bands under the towers and sometimes it dont. Is it really a tower lock or a cell lock? Only once I got it to work. Even if I set it to auto connect with tower lock, it still doesnt want to go. I know you need to have the right bands selected that the tower has.

Anyway to connect the diplayed tower/cell numbers to a website like cellmapper so we can actually see what Im connecting to? I know they have android apps that while use a LTE sim will show the tower its hooked to on a map.

I also feel like the router froze up a few times doing this and had to reboot it to get it back on. Even after unlocking the tower and using my standard band profile.