Getting error 403 when trying to use some sections in the site

I keep getting error 403 when I try open stuff in the site or sites that relates to it,

I have tendency to check this site with old FF ver so I assume the site think I'm doing something that pose security risk?

But the issue is that afterwards the error keep showing up even if I use up to date browers (such as last ver of Chrome) or clean my cookies, so I think that the site block me based on my IP or something?
I've told my RL friends to test it for me and it's working for them so it's something that only happened on my end, but only with this site.

I'm using VPN to make this thread btw to let you guys know in case it's a bug or something I did but wasn't aware of.