People stop joining server after a while.

After I restart my server people usually join within a few minutes, just a while ago 5 prople joined and everything was running smoothly. Four of them have now left and nobody has joined the server in about 3 hours. I am thinking that there is some sort of problem, but I can’t confirm anything as I can’t ping the public ip of my server from within my own network or find it in the internet tab. Could someone please check to see if my server shows up in the internet tab or tell me some way or finding out for myself?

If there is nothing wrong then could someone please tell me; why would so many people join in such a small space of time, then no one joining at all?

The name of the server is: 24/7 Sandbox [Wire, Phx3, Adv Dup, Dr who]
Map: gm_construct_flatgrass_v5
IP: 90.216.88.142:27015

People are not going to join the same server over and over. And people have lives.