Do you run Fontself for Photoshop on a new Apple M1 computer? Check this: http://help.fontself.com/en/articles/4660388-apple-silicon-windows-arm-support
Else, if the Fontself panel is not showing up it's actually not hidden, but could be prevented from running for a few reasons:
You are running an older version of Adobe apps - so just upgrade to a minimum of Illustrator CC 2015.3 (version 20.0) or newer / Photoshop CC 2015.5 (version 17.0.1) or newer.
Fontself will NOT run on previous versions like CC 2014, CC or CS6.
You don't have full admin rights in your session to properly install all files. In this case, just launch the Fontself installer from any admin session.
You don't run a fully functional copy (is it a legit official installer or a cracked one?). In such case, reinstall the latest version from Adobe Creative Cloud app.
Illustrator / Photoshop needs to be reinstalled. Uninstall and reinstall your creative app from the Creative Cloud app can sometimes fix the issue.
If nothing worked...
You will have to send us the Fontself installation logs to check what happened:
If you already closed the installer, launch it again and retry to install the extension
Once the error pops, go to "Window" and "Installer Log"
Select "Show All Logs" and click on "Save" to save it on your desktop
Just send us the Fontself installation .log file located on your desktop folder.
If it not there, just run the Fontself installer once again.
And now send us the Fontself installation logs to firstname.lastname@example.org