Rejecting connection because the server is not running?

[Pythagorion]

Greetings.
After taking a few weeks break from Plutonium, our group wanted to play a few rounds again yesterday. So we started our Windows server and wanted to join, but all the time it only said "Connecting". So I checked the server settings and ports, but everything is the same as before. I then checked the console. Besides "Sending heartbeat..." and "Heartbeat successful." it said "Received connection request from ['the players ip's'], but the server is not running. Rejecting connection".

As I mentioned before, we did not change anything on the server during our break time and the server can be started and found in the server browser without any problems, but it is not possible to connect to it. Therefore, I wanted to ask here what can be done to get the server up and running again.

Thanks in Advance.

[Resxt]

Pythagorion make sure you don't have any firewall or third party tool blocking the connections or that the port/IP didn't change. If you're using a VPS maybe you can contact their support to see if they have any idea if this could be a change on their side or something