What I'm guessing is that you can enter but can't leave your map through your portal/can't reach it? It may be because your portal coordinates aren't set?
Make sure that in the map maker, under the map section, "Has Portal" is checked. Then under "Destination Position" you just have to play with the coordinate numbers until the portal is where you want it. The way I do it is I just hover over the place I want the portal to be, look straight into the ground, and copy the approximate coordinates and yaw numbers that are in the bar at the bottom of the map maker, and then tweak it as needed.
*you can only see the portal in test mode, so you'll have to test back and forth a bit/adjust coordinate numbers to see where you want it.
If you don't set these coordinates your portal into your map can often be outside the actual map or even underneath it, where it is unreachable when tryng to leave the map.
I hope this helps ^ ^
