I was trying to experiment with PJSIP on a couple of devices. I went to advanced settings and changed sip channel driver from chan_sip to both and applied the config. I then went to applications/extensions expecting to see pjsip as an option for extensions however it was not there. Went back to advanced settings and it was back to chan_sip. Changed it back to both again and applied again and the same thing happens. Maybe its just me not understanding something or perhaps a bug, I would like to be able to create both sip and pjsip extensions on the system to try out bandwidth and quality.
You need to be running Asterisk 13, my guess is that you are running 11. Use:
asterisk-version-switch
to upgrade.