That’s strange. I tried and could not open http://openhabianpi:8080.
That surprised me because I know it worked so far.
That’s why I stopped openhab.service and started it again.
While openhab was starting, I could open http://openhabianpi:8080 and openHAB-Extension was active for a few minutes!
After openhab was fully started (which took at least >30 minutes) I couldn’t open http://openhabianpi:8080 anymore and openHAB-Extension wasn’t active anymore.
I tried that again and realized, that when openhab.service is stopped and I type in rule + <ctrl><space> a error appears.

But when I close that error (click on x) the code completion appears.
And when I start openhab.service again, http://openhabianpi:8080 and openHAB-Extension are not working anymore. Once while starting I got this error:

BTW: Always when VS Code is running, my openhab rules are executed very, very slow. This is a known issue/bug. To me, it looks like my problem could be related to this.
Edit: At the moment, openhab.service is running and I can open http://openhabianpi:8080. But openHAB-Extension is still not working. Strange!
