Shake reduction in version 2021 gives an error

I am trying to do shake reduction on a clip and it doesn't work. I get a red banner across the preview with some writing on it ...but I can't read the "error message" if that is what it is.

Can anyone tell me what I am doing wrong or at least tell me what the message in the red banner is telling me (This is NOT a user friendly message it is illegible, at least to me!!!!).

Thank you in anticipation.

Charlie