Hi, recently upgraded to the 1Gig Broadband after being with Virgin/Blueyonder for many many years.

I have many websites as I'm a web developer and noticed that some of my hosting servers are not accessible and coming back with the error of 

This site can’t be reached

I've checked the ritual things and to no avail.

Any help here please? I can access these sites via other methods outside of my home network/router.