InfoPath Dev

 Each year I have to renew my certificate from our local CA, then open a couple of Infopath forms and go to security and trust to select the renewed certificate and then deploy the form again.
I have done this on these particular forms for 5 years without any issue.
User's can no longer open the form as the certificate expired. I missed my annual reminder during lockdown!
So I open the form in Designer and it tells me the certificate is expired and to click ok to remove it, which I do.

Then I go to security and trust and check the box to "sign this form template" and then I click select a certificate.
Nothing happens. No dialogue box pops up so I can select the correct certiciate, no dialogue hiding in the background. This happens on each of the forms and now I am stuck.
I have tried running Designer as administrator, checking that my current certificate shows in Certificate Manager, I have rebooted my PC.
Any ideas? 

Yuck. I see that for me at least, the certs that I can sign a form with are in the personal certificate store. But if the cert dialog doesn't pop up at all, that can't be the issue. Want to email me your forms and cert and I can sign them for you and send them back? That would at least get you un-stuck. You can email me via the forum, I'll reply and we can coordinate that.... The only other suggestions I have are the obvious - make sure Windows updates are installed, run a repair on InfoPath....I guess you could uninstall and reinstall InfoPath....