I have a WRT1900AC since early July and I love it so far for the speed and the coverage. I have no problem with this unit so far until this week. My kids go back to school and the teachers notes and homework are posted at http://new.schoolnotes.com. We could not get to it from 3 of our computers (wired or wireless) and all of our mobile devices that are connected to the WRT1900AC. I have tried different web browers other than IE 11 (Chrome, Firefox) also with the same result. If I bypassed the router by directly connected to the cable modem then I can get to that web site without any problem. Similiarly, I can get to it at my office without any issue at all. I have reset the router to factory default and tried to go there to no avail. Convinced that the problem is in the router, I contacted Linksys tech support through their chat line. I spent 2 hours last night with their tech support changing settings in the router, security in IE, re-flashed router firmware with the same result. They issued me an RMA for a replacement.
My request to the community for anyone with a WRT1900AC, please see if you can get to http://new.schoolnotes.com and reply. I just want to be sure before I send my unit back that the problem getting to this web site is not inherent to the WRT1900AC.
Thanks for your help