It can also be cloudflare which blocks this - if you have it, whitelist your own IP.

Permissions should be correct I think, they are 775 for the folders on the files they are 664. Owner is www-data so that should be correct as well. We don't have any issues in daily use for our current forum with that at least. In the db everything points to the relative location, so the ./ Could it be the tool isn't happy with linked folders? We have our "software" files on a different location for our current forum. It's placed in a user share. But if I use that path /usr/share/nginx/groups/501st/DutchGarrison/dg_forum it doesn't do anything either. I would love to see what the output is from the location fields so I could troubleshoot this. Maybe it's doing something like /var/www/dg_forum/./uploads which of course won't work.

OK. Looks like I got it worked out for now.

That screenshot doesn't help much, unfortunately. Check your server error logs to find out what exactly that 500 error really is.

OK new issue. I tried to initiate the upgrade, but it's failing. I downloaded the upgrade files to my server (into a subdomain to house the zip file). When I try to run the upgrade it, but get this error (https://www.letsgosharks.com/forums/admin/upgrade/?controller=license&key=***) Do I need to export the files, then copy them to a specific folder?

Based on your first post, the path you should use in the first screenshot is /var/www/dg_forum, and /var/www/dg_forum/uploads for the second one (which you are already using; except the last slash). Maybe the folder permissions (CHMOD) are wrong?

What happens if you try to save the template without making any changes to it? If there's no error, the code you added is broken somehow. If you still get an error, it might be mod_security as Marc mentioned above. It's a server module, you should ask your hosting about it.

I'm just trying to add another link to the navigation. Nothing much different to what the file already contains. Just another list item with a link. I'm not sure what mod_security is. Pretty new to this software. Where can I check that and what exactly would I be checking for. Thanks