Thank you for reaching out and sorry for the trouble.
1. As you trying to create PDF from third party software, could you please let us know the error message you are referring to? Did you try creating a PDF from Acrobat application directly? Or you are experiencing issues in opening those PDFs? Please elaborate.
2. As all the thumbnails appear as blank, would you mind sharing the screenshot with us? Also, please check if the option "Enable PDF thumbnail preview in Windows Explorer" is checked under the Acrobat Preferences.
3. "In the Adobe Creative Cloud panel, the Acrobat Pro DC thumbnail is black and white": Please share the screenshot with us.
There is a change in the Acrobat icon with a recent update. The new icon has a black background and a white logo.