Having encountered a variety of weird Internet problems similar to yours, I will offer the different methods I use that tend to clear up the issue. My knowledge of why they tend to work is at best intermediate, but they tend to resolve issues:
The order is unimportant, as is doing all of them. Any one or a combination of several of them might do it.
All from the command prompt:
:: resets the ipv4 interface
netsh interface ip reset
:: flush and reregister DNs
ipconfig /flushdns
net stop dnscache
net start dnscache
ipconfig /registerdns
:: clear persistent routes
route print -f
:: start / restart mrxdav
net stop netbt
net stop mrxdav 2>nul
sleep 60
net start mrxdav
net start netbt
:: clean the arpcache
arp -a -d
:: I might have the order of the switches backwards and the order matters, so if that doesnt do anything put the -d before the -a
:: make sure winhttp and webclient services are running (this is a mystery to me / neither appear necessary, but both have fixed my problem on various occasions)
net start webclient
net start winhttp
Finally if still not fixed, restart router and the restart pc. It won't tell you what is wrong, but it will almost certainly fix the problem.