Unable to change font style on Mac Mail Note

In Mac Mail I opened a Note (yellow pad note) and worte some text.

I want to bolden the text and change some of the fonts - but no editing is accepted.

When I click Command+B, I hear a 'thud' sound and nothing happens - as if editing is blocked.

Also unable to select any text and change the font using the font selector.

Has anyone ran into this before, what should I do - I think I need to reinstall mac mail, but I don't know how.

Thanks