Signature Line - Cannot use certificate to sign

Hello,

I work for an IT support section and am having difficulties with resolving an issue with signature lines.

Error when clicking Sign.

The users have recently received new Windows 11 devices with Office 365 enterprise applications installed (Excel, Word etc.). Signing signature lines on Excel workbooks worked when they were on Windows 10 on their older devices. They had generated user certificates on their previous devices that were able to be used to sign signature lines with. I've used our Networks trusted CA to publish new certificates to the Personal > Certificates on the current user certificates. I've done this the same way as I did when on W10. What I've found is that the certificate is able to be used to sign documents in Word but not Excel. 

Version of Office: 

I have found the following error in the diagnostic log for Excel relating to the error code -2147418113 which the Microsoft error code tool advised it was a Catastrophic failure referenced as "E_UNEXPECTED".

None of the information obtained so far has helped me fix the issue. The only clue I can see is htat it works in Word and not Excel. Can anyone advise?