Octoprint server not running after connecting to a new router

Hello everyone,

After changing my rooter, I reconnected (Wi-fi) my raspberry , and I can access it with the IP and SSH.
However, I get the error on my browser " The OctoPrint server is currently not running".

Verify that the process is running: ps -ef | grep -i octoprint | grep -i python should show a python process

It doesn't do anything for me, not even an error.
The logs stopped when I disconnected the raspberry yesterday and nothing new would show up since then.

I tried this also :

sudo service octoprint restart

But it didn't solve my problem.

Currently running on :
OctoPrint version : 1.3.9
OctoPi version : 0.15.1

Last logs I had :

2018-08-23 12:01:08,007 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 12:16:08,010 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 12:31:08,013 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 12:46:08,016 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 13:01:08,018 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 13:16:08,020 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 13:31:08,023 - octoprint.server.heartbeat - INFO - Server heartbeat <3
2018-08-23 13:46:08,025 - octoprint.server.heartbeat - INFO - Server heartbeat <3

I'm very new to this, and it wasn't me who configured the raspberry on the old rooter.

Any help is welcome, thx !

It might be worth running a df -h to make sure that your root volume isn't full.