Port 80 is closed on CAX30

Hi,

I'm trying to forward port 80 from my CAX30 modem to my laptop and it is not working. I was able to forward ports 443, 18080, etc. but for some reason port 80 doesn't work. I don't have any Access Controls turned on. The way I'm testing is, configure port forwarding rules for the above ports, finding my modem's IP on the internet, using that IP on my mobile phone (with wifi turned off) along with each of the above ports. Mobile is able to load contents for ports 443 and 18080 but not for 80. And when I used this site: https://www.yougetsignal.com/tools/open-ports/ to check the above ports, it shows that port 80 is closed, although I have configured it the same way the above ports were configured. I even tried restarting the modem a couple of times, but no luck. 

Is anyone able to shed some light on what I could be doing wrong here. Greatly appreciate any help. 

Edit: I am on Optimum ISP and I have enabled traffic on port 80 on their website as well. 

Thanks,

R