"Not checked in"

I couldn’t find a problem simular to mine, so I decided to create a new topic.
Recently I created a first lay-out to use in our veteraniry clinic. I downloaded Xibo for Linux, bought a licence and signed up for Xibo in the cloud. I checked everything at home and it worked fine.
After moving everything to the clinic I found out the status of the display kept saying “Display is out of date but has not yet checked in with the server”. The player is connected to the internet and the internet is working fine (cabled). So took the player home again and connected it to a monitor to test: suprisingly at home everything worked fine again. So I went back to the clinic and installed it all again. I signed into the CMS on a computer and I was happy that it all worked! But… while working on the clinic I discovered the connected failed again when I tried to update the layout. The display only updated and made a good connection when I switched of the player and started it again. A problem I don’t have at home.
Since I left the clinic I can’t reach the display anymore from home, eventhough I’m 100% sure the player is connected to the internet.

Does anyone have this problem aswell? Or is there a topic with the answer?