Why won't my Captivate (2019) files sync to OneDrive?

One Drive keeps offering to rename my Captivate files because they have 'invalid names'.  This *appears* to be because they have a space in front of them.

Trouble is of course that once they're renamed Captivate doesn't recognise them any more.

(I'm new to Captivate, I have a stand alone copy on my Wondows 10 PC and that backs up automatically to OneDrive)