iOS apps cannot connect to ABS server on same network

I'm losing my mind here. I have a server running just locally for now through Portainer on Docker Desktop, I can access it on the web browser just fine on localhost:13378 (I do know the IP address for localhost). I have port forwarding set up on localhost for port 13378. I even have a static IP set up for the computer the server is running on as the IP for localhost, and I don't have a VPN on. I don't have a reverse proxy or anything set up so I just HTTP to connect. I'm no network whiz, far from it, so basically all my info is just following instructions on the documentation.

For a while my iPad and iPhone could connect to it through Plappa just fine while on my home WiFi. Then one day, iPad just kept saying "couldn't connect to your server". I checked my settings, everything was okay, but couldn't connect and wouldn't sync anything. I logged out figuring a log back in was fine, but then I couldn't log back in--whenever I tried, using http://{localhost IP}:{port}, it would hang for a bit and say the connection timed out. I thought maybe the Plappa app had issues, and I wanted to swap to Shelfplayer anyway, so I downloaded that and attempted to connect. When I go to "Add Connection" and supply the URL and hit verify, it also hangs and then just... doesn't do anything. No notification of successful verification, no option to authenticate or anything. Now the Plappa app on my phone says it can't connect to the server and won't sync anything. Attempting to connect to the URL on my phone browser just returns a "Site cannot be reached, request timed out" issue.

I don't know what's going on, I don't know why it worked at first and isn't working now. I've updated Docker, reinstalled portainer, and completely reinstalled/composed the ABS container. Nothing is working. Any help would be greatly appreciated.