The device state of this queue member, ... , is still 'Not in Use' when it probably should not be!

I’m getting LOADS of these warnings:

WARNING[12953] app_queue.c: The device state of this queue member, Local/30@from-internal/n, is still ‘Not in Use’ when it probably should not be! Please check UPGRADE.txt for correct configuration settings.

Anyone can explain what it means and help me fix it please?

Thank you.

I’m sorry i forgot to add a description of my system:

1 freepbx server with latest asterisk, 3 extensions (10, 20 , 30) and 1 queue which includes all three extensions as members.