What usually causes a 603 error?

Question

Asterisk

Good evening people
Tell me who is not difficult. When I make an outgoing call, I get eio
-- Executing [[email protected]:2] Dial("SIP/305-000001d3", "SIP/[email protected]") in new stack
== Begin MixMonitor Recording SIP/305-000001d3
== Using SIP RTP CoS mark 5
-- Called SIP/[email protected]
-- Got SIP response 603 "Decline" back from 212.116.247.5:5060
-- SIP/ducat-000001d4 is busy
== Everyone is busy/congested at this time ( 1:1/0/0)
-- Auto fallthrough, channel 'SIP/305-000001d3' status is 'BUSY' == MixMonitor
close filestream (mixed)
As usual, everything worked before, right now with the main provider, I wanted to throw the trouble and got stuck. Tell me why this usually happens and where to dig

Answer 1

The last time I caught such an error was on the E1 channel, when the outgoing number CALLERID (num) was not specified before the call.