Hi Nir, all you should do upon receiving B's REGISTER, after saving the contact (by calling save function) is either resume the transaction, perform a lookup and relay or call ts_append (if you already relayed the INVITE). If you get "unavailable" (I guess that this means that you are receiving a 404) probably the user is not being found in the location. Check if you are doing these steps in your config and if it doesn't work try to send the relevant part of the config and the kamailio's logs. I'm currently away and almost without network but I'll try to have a look as soon as possible. Regards, Federico On 21 Jul 2016 16:09, "Nahum Nir" &lt;hello.shalom.hi(a)gmail.com&gt; wrote: Thanks, I was able to suspend the transaction and wait for the register but the client that sends the INVITE get unavailable right after the other side joins. Here is my debug flow: Client A sends the INVITES. Use case 1: Client B register one time. Then I turn off the WiFi in client B so it will not recieve the push notification. Client A sends the INVITE, server sends the PUSH and Client A is waiting for 5 seconds. Use case 3: Same as before but now client B get the push. This time client A that sends the INVITE gets from the server unavailable as soon as client B register. I did as you suggested and suspend the trunsaction before sending the push. Probably a second suspend is needed when client B sends the REGISTER? Thanks and regards, Nir On Wed, Jul 20, 2016 at 4:06 PM, Federico Cabiddu < federico.cabiddu(a)gmail.com&gt; wrote: