Importing New Font

What is your intent? You shouldn't be using Acrobat to do any major editing. If you just want to do spot edits to an existing PDF that uses that font, that's fine, but for anything else, you should look at a better approach to create your content.

You don't import fonts into Acrobat. Font Book controls the fonts for your entire system, with the exception of those activated from Adobe Fonts through a Creative Cloud subscription.

That being said, there are some fonts native to a Mac that Acrobat has problems "seeing" and those are the .ttc (TrueType Collection) e.g Helvetica Neue. These .ttc fonts contain more than the usual 4 font styles (Regular, Italic, Bold, and Bold Italic) and this confuses Acrobat.

Also, if you have recently installed a new font, make sure you've restarted Acrobat so it knows it's there.