Gitlab runner fail due to some HTTP error

I have recently set up runners for my gitlab instance.
However, these runners seem to fail every single time for my projects. I was wondering why, and the error is as follows;

Now, my gitlab is exposed to a certain port, and I use Nginx proxy manager to force SSL (Aka, force HTTPS) for anyone using it, so if you go to http://gitlab.blahblah you will be automatically redirected to https.
When I turn this feature off, the problem seems to go away, however, I would like to keep it on because it imposes security measures. Is there something I can do?