T.38 Fax Issue

I have added the Fax Support license in the Asterisk with FreePBX GUI. I can place outgoing T.38 fax calls without issue. However, incoming fax calls do not seem to detect any tones and simply drop. I am expecting the incoming (from PSTN) faxes to be detected and switched to T.38 from the Asterisk PBX. But, it does not happen.

What am I missing?