As the error message states - there is an issue with the template for that extension. To get rid of the error you need to find the template issue - also mentioned in the error. It is balking at hpbx_http_port.
I use an unsupported phone and need to keep the templates up to date myself. It looks as though
I see the problem that you are pointing out and I was able to find the proper variable from one of the built in templates, thanks. However 3CX better update their documentation because on this page:
I respect that keeping the documentation upto date is a big job. What would at least make it easier for us lowly users was if you stated on the page what version of the software this was pertaining to, then atleast we would know.