My rig is remote so as along as it keeps hashing I try to avoid router reboots, DNS changes (clearing cache), but given you have them locally, I would try google DNS if not tried already, rebooting your router and ofcourse checking if you dont have cloudfare ban. From the chat with SMOS moderator yesterday:

my rig isnt shown in dashboard or as OFF?
1.power failure / internet outtage (check internet connection and if rig is working)
2.pendrive coruption - boot rig and see if it is booting properly, connecting to simplemining and starts mining
3.pendrive corruption/ rare case - sometime email can revert to its original “admin@simplemining.net” - check if you have your email in config or is the file corupted
4.cloudflare ban (to check this you need to enter simplemining.net website and see if there is some kind of block message or captcha to solve)
5.dns problem - your ISP problem, you can solve this by using google dns (8.8.8.8 & 8.8.4.4), also you can reboot router to see if that helps.