Graph view issue, it disappears

What I’m trying to do

see below

Things I have tried

As a newbe to Obsidian it is hard to do any special.
So I just restarted my McBook at least.

I searched anything in the help docs about Graph view. But this wasn’t really helpful. So, there were no solution suggestions on my issue of Obsidian.

What is happen:
Graph view disappears: I have activated TAG in the graph setting (filtering graph view using tag:#mytag). Since then, the graph view only appears for half a second, then the graph disappears from the screen, leaving only a black window.

Unfortunately, this unwanted behavior is now permanent!
Even after deactivating TAGs, closing and restarting Obsidian - and even restarting my MacBook. No change.
What can I do? Before activating TAGs, the graph view worked perfectly.
Thank’s in advance.