server runs, cant join.

(SOLVED)
i made a server so i can play with my online friends, the problem?
well, its there, seems fine on the list, but when anyone tries to join (including me):this only applies to this server, a friend who used to host had this problem too but got it fixed, i cant seem to figure it out.

premium didnt fix it

we have tried multiple launchers for minecraft, made sure we were running the correct version, we just get a reworded message, but the same thing.
only applies to this server, every other server works fine.

i figured out out, i had to run it in cracked