Digital Signature and Digital Certificate Signing are not working

[hani_HFK]

Hello All, 

I need your help, Topic: signing PDF File in Acrobat using Digital Certificate on MAC Pro Computer

Signing with Digital Certificate doesn't work; and it always give me: [the Credential selected for signing is invalid]... attached file.

Attached is my Digital ID and Trusted Certificate as it is registered in Adobe Acrobat ... it seems all good; but i can't sign digitally or Certify any PDF file (even plain text letter).  

I need your help please.

[creative explorer]

@hani_HFK The error message about the credential being invalid can sometimes point to a mismatch between the certificate and Acrobat’s security settings, or even a permissions issue on your Mac. Unfortunately, I can't duplicate this error message on my end as it works perfectly fine for me... which of course doesn't help you. 

You can try the following then:

• Even though your certificate looks valid (not expired and properly issued), Acrobat might not be using the correct one for signing. Try manually selecting the certificate again when signing, and make sure it’s the one listed under “Digital Signature” and “Non-Repudiation” usage.
  
  
• Since your certificate is stored in the Mac Keychain, Acrobat needs permission to access it. Sometimes, macOS security settings block this. You can check this by opening the Keychain Access. Look for your certificate. Right-clicking it → Get Info → Access Control tab. Make sure Acrobat is listed as an allowed app, or set it to “Allow all applications to access this item” temporarily for testing.