Jellyfin randomly stops allowing connections

[Venson]

That sounds like you forgot to add the port forwarding rules for the ports jellyfin uses in your firewall on the PC.
The default port jellyfin uses is 8097

I originally set it up and it worked, I already have firewall exceptions set up.

After some investigating I found out that my computers internal IP changed(?) So I had to remap it.

Yes that may happen. Check if your router allows either Static DHCP mapping for your PC or if you can set a custom DNS record.
What router do you have?