Cannot connect to some MC servers

So, basically sometimes when I type in a different server I want to join it doesn't work for me but for my friends it does. Sometimes it works to join 1 server and sometimes it doesn't. For example I was on a server at another house and I was playing it for 2 days straight. I come to my home and I try to connect to it, It doesn't let me connect at all. PLS HELP ME SOLVE THIS