1-)Make sure you filled in the correct IP and subnet mask.
2-)Disable anything you did on the static routes that youve entered the static IP address for, delete them if possible.
3-)On the WAN > Internet connection page if you have entered anything on the Static IP Alias (or something like that) table, delete them too.
So you only want your IP only entered on the LAN page, under basic settings. Youre gonna come across a page where you have the default settings for the router 192.168.1.1 / 255.255.255.0 etc...
Right below that is a space where you can enter additional IP adrees...AKA the address assigned by your ISP to configure on your webserver.
Punch those in and waheyyy bobs your uncle and tiffanys' your aunt.