Can't install this extension because Safari Extension Disabled

[cormullion]

I can't seem to get this extension to appear in Safari preferences:

Any tips?

Safari Version 18.6 (20621.3.11.11.3)
MacOS Sequoia 15.6.1

[ACTCD]

• FAQ and How to Review Error Logs 常见问题和如何查看错误日志 #409