Transfer external call not working (suddenly)

[Duelund]

Suddenly we can not transfer incoming calls anymore.
We are using 3CX v10 SP5 and SPA921 phones.

The one you try to transfer to, just get music (onhold).

Any ideas ?

SP 4/5 ?

 

[Duelund]

This procedure (Attended transfer method) is not working anymore:
http://www.3cx.com/blog/voip-howto/blind-attended-transfer-cisco/