Magic Mouse not highlighting text in word

My mouse just recently stopped highlighting text in word. It highlights text in other MS apps like outlook, teams, ppt and excel and in word online but not in the desktop version.

I haven't changed anything recently so I don't know why it has suddenly stopped.

I did a factory re-set on the mouse - no change - but since the issue is restricted to word app only, I don't think it's the mouse, or is it?

Thanks