The new version (10) does not work with fonts activated through Adobe Fonts! This was not a problem with version 9 and needs to be corrected.
This Article may be relevant.
Since I don’t use Adobe products, I might be mixing up two different things.
No, the article is not relevant.
I am not referring to a plugin that automatically activates fonts for specific applications. Rather, I am referring to fonts that are activated through Adobe Creative Cloud that allow fonts to be used for ANY application on one’s system until deactivated through Creative Cloud. The fonts show up as activated (red button) in MainType as they did with previous versions, but the new version 10 does not display sample previews (or character maps, etc.) of those fonts.
I think the behaviour is the same with version 9 and 10, as both did not show such fonts in the Sample and Characters panels.
You are indeed correct, sir! I uninstalled version 10 to revert back to version 9 and it does not show character previews, either. 
This should NOT have been reported as a bug!
I moved the topic to the Support forum.