Can't call outside numbers

Hi. I’m new to the Asterisk.
I’m configured two TDM400P cards. and everything was working until today.
I have 6 pstn lines with 6 different phone numbers. When i try to call out it calls only trough one line. If 3 callers trying to call out one of them getting busy tones so his calls don’t go through. Can any body help me to find my configuration mistake?
Thank you!

Asterisk 1.8.11.0
FreePBX 2.10.1.1