The Windows Cryptographic Service Provider reported an error

I don’t know if this is the right channel since this is a very technical topic; if this is not the correct place, I would appreciate information about where to ask this question.

My company has developed a CSP (Microsoft Cryptographic Service Provider) and a CNG KSP (Key Storage Provider) that perform signatures using keys stored by one of our products. Both the CSP and the KSP work correctly, but when I try to sign in Acrobat using a certificate associated with the CSP, it works fine; however, when I use a certificate associated with the KSP, nothing happens and no error is shown when pressing the Sign button.

If I disable the “modern user interface” checkbox, it gives us a clue about the problem because it displays the following error:

The Windows Cryptographic Service Provider reported an error:
Access is denied.
Error Code: 2147942405

I followed these instructions but the error still appears:
https://helpx.adobe.com/es/acrobat/kb/windows-cryptographic-service-provider-error-214794205.html

In my KSP logs I can see that it only executes the GetKeyStorageInterface and OpenProvider methods, but it does not call any other method.

Only if I disable the “Enable Protected Mode at startup” checkbox does the KSP work correctly, but we cannot force our users to do this. I tried enabling the “Create Protected Mode log file” option, but it does not show any error related to the KSP.

Any idea how to find out the cause of the error or a possible solution?

Thank you very much.