If the browser extension is unable to be installed or does not appear on the Safari extension list after installation, you could troubleshoot by the solutions below.

Note: It's known bug in Safari 14/15. We have reported it to Apple, but haven't received their reply yet.

Solution A: Running the command to restart extension services in Safari

Close Safari Browser, and open Terminal.app
Running the below command in the terminal and restart your computer:
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
Open Safari again. The extension should appear in Safari

Solution B: Install the Safari Technology Preview

Close Safari
Download and install the Safari Technology Preview
Open and close Safari Technology Preview
Now extension should appear in regular Safari

If the issue still persists after the solutions above, please do not hesitate to contact us

Safari Extension cannot be installed or not appear