I have installed the Weatheroclock@CleoMenezesJr.github.io extension. I have enabled if via the Firefox browser however it's not showing up. How do I correct that?
It may require a logout before showing. Otherwise you need to open appearance --> taskbar settings and rearrange stuff.
In the Describtion stands that Gnome Weather is required. Do You have it installed? If not, You can install it with the Terminal Command sudo apt install gnome-weather
So, you installed it with the Gnome Extensions Website, yes?