u/Purple_Degree_4008

https://preview.redd.it/x2i0wt5xs5wg1.png?width=444&format=png&auto=webp&s=be96312f51d3c307e8c1b8470d9abff9fa1378fa

Whenever I try to add an extension, I get the same error message http error 404
Is there a fix for this?
(I really dk what im doing so apologies if im being a bit stupid at all)