I recently encountered a problem with a website I was working on. I stopped being able to access the site. All my browsers were not able to connect to the server. I was able to access all other sites that I needed.
I contacted the host of the website and requested that they check my ip address had not been blocked on their end which they did and it didn’t help.
They suggested I check my ISP. I then tried to access the site using my mobile phone on the same wifi network and this worked fine.
After some time I realised I had set up a server using MAMP Pro using the same address as the site which I had forgotten about. This was stopping me accessing the site. Once I changed the name of the server I set up, I was able to access the site without any problems.