DT Pro won't import bookmarks nor contacts

[BLUEFROG]

Have you allowed access for DEVONthink to Contacts in System Preferences > Security & Privacy > Privacy?
You should also allow Full Disk Access and any Automation requests DEVONthink makes.

Regarding Firefox, Full Disk Access may help, but it handles its bookmarks in its specific way. This may help as well…

Firefox bookmarks do not appear

This is an issue with how Firefox stores its bookmarks. But there is a setting that will export Bookmarks to an HTML file when Firefox quits. In Firefox, type about:config in the address bar. Click the button to accept the risk. Search for Bookmark Double-click the line that reads Browser.bookmarks.autoExportHTML. The value should be set to True. Quit Firefox. (I actually suggest relaunching and quitting it again, just to make sure.) Attempt the import of Bookmarks into DEVONthink.