Call back (camp-on) not working

I have Asterisk 13.9.1 with FreePBX distro

I am trying the following: Extension A calls extension B. But extension B is busy. So extension A hungs up and then press *82 to request call back (camp-on request). Unfortunately call back is not initiated.

I have enabled camp-on on settings. I have tried with call waiting enabled. and call back is not initiated.
(I tried at first with call waiting disabled, which is what I prefer, but still call back is not initiated.)

On both attempts I get a weird message on the logs:

[2016-12-29 22:54:47] WARNING[4586]: res_pjsip_pubsub.c:2968 pubsub_on_rx_publish_request: No registered publish handler for event presence
[2016-12-29 22:54:47] WARNING[13643]: res_pjsip_pubsub.c:625 subscription_get_handler_from_rdata: No registered subscribe handler for event presence.winfo

Please help,

IIRC, camp-on only works with SIP (not PJ-SIP).

I also remember something about camp-on being deprecated, but that might have been in a nightmare…

thank you very much for taking the time to reply.
This is a live system, and all the extensions are using PJSIP on port 5060.
In order to change them all to SIP 5060 I have to change the listening port of PJSIP and SIP on the live system. Is it doable?

Asterisk has removed support for Camp On. I suggest not trying it as FreePBX nor Asterisk will fix any of the many bugs in it.

and how can I implement the call back on busy?

You can’t. It doesn’t exist except camp on and only with chan_sip and is not even supported anymore