Access to notes on different devices (sync)

My version of HedgeDoc is: 1.10.3

What I expected to happen:
I’ve only started using Hedgedoc very recently (1 month) and it has been a good experience using it for my notes in my browser (firefox) on an Ubuntu device.

What actually happened:
A few days ago, I had trouble accessing my notes with the error “Problem loading page”. It seems like the server (https://hedgedoc.jnwlabs.com) can’t be accessed during certain times of the day as this morning it worked again but the same issue occurred in the afternoon.

I already tried:

Using different browsers (firefox, chrome, microsoft edge). Logging in on another device, however, my notebooks don’t seem to be synced to my account so it is only blank. Uploading history doesn’t work (although it doesn’t have the content anyway). I saved the notebooks but I want to edit them rather than just read them. Access through the link results in the same issue.

Appreciate any advice and support, thanks.