We apologize for the delay in response to your query.
The password protected pdf document you are referring here, what is the trouble that you were experiencing when you were trying to open it?
Is it not giving the password box or when you entering the password its not accepting it?
You may refer to the forum thread https://forums.adobe.com/thread/2062404 is it a similar issue discussed in that?
If I enter the password it is not accepted so it ask for the password again this happens only if the pdf is downloaded from eMail. If downloaded and copied to, for example, the cloud and downloaded from there it works fine.
Hans van Noort
[details removed by Ussnorway]