Acrobat Pro incomplete popup digital signature list

[Norber_RM]

I'm using Acrobat Pro, Spanish version, on MacOS 13.5.1 - Apple M2. Under Preferences-> Signatures-> Identities and trusted certificates->  I have 11 valid digital signatures. When I try to digital sign a PDF, Acrobat only offers a list containing 8 items, not the 11 I have installed. The same happens when disabling the "modern" inteface: the traditional popup shows only 8, not 11 items. Where would be the problem? Thanks

[MikelKlink]

Adobe Acrobat only supports certificates with certain combinations of KeyUsage and ExtendedKeyUsage extensions. See here for reference. Possibly your 3 missing identities deviate from those requirements.

[Norber_RM]

Thanks for your hint, Mikel. Unfortunately I've not been able to locate where can I check the compliance of any certificatewith KU extensions. Where can I look, please?

[Norber_RM]

Sorry, but I've just noticed some minor difference that could be related to what you suggested. Under the "Uso deseado" (intended usage) the certificates that do show up in the list include "Protección de correo electrónico" (email protection) and the certificates that do not show up lack of that mention. Could it be the issue?

[MikelKlink]

If you follow the link I posted above, you'll see that EmailProtection indeed is one of the accepted ExtendedKeyUsage values.

And the field you found shows both the KeyUsage and the ExtendedKeyUsage values of the certificate in question. 

Thus, indeed, that can be the issue.