How to get rid of "keying set failed to insert any keyframes" error


I am struggeling with the NLA Editor.

It seems that I am triggering a (for me) strange Hotkey, which keeps me from adding new keyframes.
The last times I noticed it before saving, unfortunaltely, this time, it was already saved closed.

Whenever I try to add a new keyframe I get error messages.

When I try to add a loc rot scale keyframe I get “keying set failed to insert any keyframes”
When I try to add a constrains keyframe I get “could not insert keyframe due to zero NLA influence or base value”

I tried all tipps, I found in the net, but nothing helps.

I checked the Scene Properties, but there is no keying set defined.
I checked also the Active Keying Set properties in the Timeline. There was also nothing specified.
I tried there other settings like LocRotScale and others. but no result.

What did I do, to get to this state and how do I get rid of it.

Got rid of it. I did not see that little pin symbol on the track