Can’t connect

What is that I can’t connect to my friend server and my friend can’t connect  to my.

first I buy fucking maincraft and I can’t play with my friend ,late I am buy FUCKING REALMS PLUS AND IIIIII CANT PLAY WITH FRIENDS WHAT IS THAT . You have this problem many years and you can’t fix that.
I will be forced to go to court because I gave my money for some unknown reason