Module Dulicates and Missing installations

Hello,

I have two issues with my opencart at the moment and I'm guessing its potentially the same fault.

Firstly, in the Extensions page every module is shown twice - mirrored on the same page

Secondly, any installed module/theme doesn't show up in Extensions.

Any advice would be very much appreciated.

I've recently updated to 2.3.0.2

Have you upgraded your store from previous version? Because it looks like you did.

Try to download and install OpenCart 2.3 Compatibility Fixes extension from the extension store. Don't forget to go to User Groups and set access/modify permissions for all extensions. Should help.