Missing "add new" button

Hello everyone,

I need help with a wordpress plugin related problem.
I am not new to wordpress, have some experience but I wouldn’t exactly call myself an expert (which is why I need your help). Recently I came across a problem with the extensions page and I can’t find a solution nowhere in the forums or the internet.

So I have a wordpress website to wich I would like to add a new plugin. Simple enought, right? I know I cann add a plugin by either clicking on the “Add new” button on the extensions page OR via the FTP which I have already done a few times. My problem is that the “Add new” button on the extensions page has dissappeared and I cannot upload a new plugin via the FTP. I find this really strange as the plugin appears on my server, but it doesn’t show up on the wordpress plugins page.

I have already installed an older version of my site from a back up that I had made when everything was working fine, exept this doesn’t seem to resolve the problem either. So then I have tested the site on local the latest version of my website and the button appears and is working correctly.

Would anyone please be able to explain this to me? That would be great! You would really help me out in work as I am deparate to finally find a solution. This is driving me mad ??

Thanks in advance ??