Excel's Ribbon irregularly dissapears/greys out!?

[WesselTelco]

Can anyone help me out with this strange error?

More and more colleagues are having the same issue where when they open an excel it works perfectly fine, they have the ribbon and menu above. But when they open another file the complete header greys out, there's no menu or ribbon.

See attached screenshot of a file to the left which works perfectly fine, and the other file to the right missing the header.

I tried to reinstall office, but the same problem occured.

I hope anyone can help me with this!

Thanks in advance,

Wessel

[#2]

I've seen this happen too the other day. What got me out of that state is opening the File menu by hitting alt+f. I suspect some VBA action sometimes causes this, but I'm not sure.

[#3]

Hi Jan,

Thanks so much for your reply.
I tried your suggestion, yet still nothing changed unfortunately.

Thanks again,
Wessel