Happy Christmas !

I wonder if anyone has any clues to this odd behavious in Excel 365, please ?

My Excel installation seems to be fine - several complex Workbooks with many macros are working just fine.

One, though, is not. Here are the symptoms . . .

1. Macros assigned to text-box buttons work as expected
2. Macros assigned to Worksheet code eg Private Sub Worksheet_Change(ByVal Target As Range) are not being triggered
3. When I go to the list of Macros using the button on the Developer tab, none are visible and all the options in the dialog which opens are greyed out.
4. When I open the VBA environment using ALT F11 and go to Tools . . . Macros . . . I get error Unexected error (35005).
5. However if I go to Project Explorer, the Macros are visible as usual in Module1

Grateful for any ideas where to start looking for the problem.

Thanks