Problem with connecting to server with more than 5 players

When I try to connect to server there is a error:
io.netty.channel.abstractchannel$annotatedconnectexception
It seems like this server has player limit set to 5. Obivously player limit there is 30 so I don't know why is this happening. Everyone trying to connect is having same problem .BTW i'm on 1.15.2 \
Please help