We’ve implemented a few FreePBX servers, but have never run into this issue before. When an extension has Follow Me disabled, there is no problem calling that extension from another extension. However, when Follow Me is enabled, we get a busy signal and the logs show this:
[2018-07-06 15:31:14] WARNING[C-00000003] pbx.c: Channel ‘SIP/1-00000003’ sent to invalid extension but no invalid handler: context,exten,priority=followme-check,2,1
Everything is set to default - this is a brand new installation of FreePBX on the latest distro (12.7.5-1805-3.sng7).
The follow me list shows the extension, and then an external number (followed by #). I’ve tested removing the external number and just having the extension, and I’ve tested without the extension and just the external number. All result in the same log entry as shown above.