When I navigate to the URL math.stackexchange.com on my home internet, I receive the "We are offline for maintenance" webpage. This does not happen for any other Stackexchange website, as proven by my being able to write this question right now. It has been like this for several days, and began when there was some sort of maintenance 4 or 5 days ago. I have cleared my cache and all other browsing data, and I also receive this message on my mobile device if I'm connecting to my wireless network.
However, if I use the cell network to connect to the internet, I can visit the website just fine, and similarly with my office internet, I can visit the website.
Is this clearly a problem on my end, or could it be a problem with my ISP? Does anybody have suggestions?
EDIT: I did one further test and found that it cannot be my ISP. I set up a proxy to another server, and then ran my browser through that, and I still got the "We are offline" message. This gave me the suspicion that it might be my router, and indeed, upon resetting my router, I could finally visit math.stackexchange. So now, my updated question is: How did this happen?