Cannot configure Find Me Follow Me to fallback to voicemail

I have set up an extension to use FMFM.   When the extension is called, the phone rings "Initial ring time" seconds.  After that time, the only number I have in my "Follow-me list" is a cell phone.   The cell phone rings as expected but continues to ring regardless of the time set in "Ring Time", with the following exception; If the "Ring Time" is set to 2 or 1, the cell phone does not ring.  Any number greater than 2, the cell phone rings until the cell phone's voicemail answers.  Approximately 15 seconds.  I want the FreePBX voicemail to take the call if it's not answered within "Ring Time" seconds.

I have tried countless combinations of settings in the "Initial Ring Time", "Ring Strategy", "Ring Time" and "Follow-me List" without any success.