Internet connectivity issues are very common. Fixing them mostly involves several steps that should be taken in order to make sure where the problem lies, beginning from checking network settings, trying different DNS entries to router connectivity, tracerouting, et cetera.
Should we have a Community FAQ on this?
I searched a bit, but couldn't find any related CW or really popular question.
I could imagine this would work similarly to the What to do if my computer is infected by a virus or a malware? question. We'd then be able to point the OP to our new CW and make sure they try all the steps outlined there – yet not just hastily close all questions as a duplicate. This would save us a lot of answering with the same steps all over again or commenting with request for more details.