"Connection Timed Out" on CanYouSeeMe.org for port 80

[g-14523]

I'm trying to port forward port #80 for a website, but I keep getting "Connection timed out" messages on canyouseeme.org. I've already added a rule for my firewall for this port, and I'm sure I did it correctly. I'm running Linux Mint 18.1 on this PC. What should I do?

Edit: Recently switched ISP's, port forwarding on the old ISP always worked, but with this new one, doesn't, so I assume this has something to do with my ISP?

 

[beers]

Some ISPs filter 25/80/443 inbound to prevent spam and 'at home web hosting' services.

You can try the same settings on another port such as mapping 8888 on the outside to 80 on the inside, if you can see it as open on canyouseeme.org after making the same firewall exceptions and configuration then it's blocked at an ISP level.