OpenHAB suddenly down?

The day before yesterday I added a Unifi G5 Bullet camera through the UI (I had installed the Unifi Protect binding a few days earlier). That was the last change I recall making to openHAB.

I received a notification in my Android app as late as this morning.

And now I can’t reach my openHAB server in the browser anymore, and see this when I SSH to the machine:

erik@MinipcLG2:~$ sudo openhab --help
sudo: openhab: opdracht niet gevonden
erik@MinipcLG2:~$ sudo openhab-cli console

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See for further details.
SLF4J(W): Class path contains SLF4J bindings targeting slf4j-api versions 1.7.x or earlier.
SLF4J(W): Ignoring binding found at [jar:file:/usr/share/openhab/runtime/system/org/apache/karaf/org.apache.karaf.client/4.4.6/org.apache.karaf.client-4.4.6.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J(W): See for an explanation.
Logging in as openhab
Failed to get the session.
erik@MinipcLG2:~$ apt list --installed | grep openhab

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

openhab/stable,stable,now 4.2.0-1 all [geïnstalleerd]
erik@MinipcLG2:~$ ls /etc/init.d | grep openhab

Pi-hole runs on the same Linux machine and works without problems.

Anyone any idea for a troubleshoot?

Thanks in advance!