This issue happens with Universal Type Client 7.0 and 7.0.1 for Mac OS and Windows, and Adobe Illustrator CC 2018 or earlier, Adobe InDesign CC 2018 or earlier, Adobe InCopy CC 2018 or earlier, or Adobe Photoshop CC 2018 or earlier.
When you open the Extensis font panel in Adobe Illustrator, Adobe InDesign, Adobe InCopy, or Adobe Photoshop, the panel is blank. The first time you open the font panel in Adobe Photoshop, you get an error dialog stating the “Extensis” extension could not be loaded.
The Adobe Creative Cloud applications will not load an extension that is not properly digitally signed; the font panels in Universal Type Client 7.0 and 7.0.1 were digitally signed with a certificate that expired on February 11, 2019.
Universal Type Client 7.0.2 and later includes font panels were signed using an updated digital certificate. You can get the installer for the latest version of Universal Type Client from: