I am having a similar issue with the same printer, also I am brand new to printing so wanted to rebump this thread to see if there are any further suggestions.

To add to the discussion, my printer starts out fine for the first and maybe second layers, then extrusion tapers off suddenly and no further filament is extruded. I have taken apart the extruder and am not seeing any distortion to the feed as displayed by the original poster.

This problem also seems to happen quicker as I make repeated attempts which leads me to think it is heat creep related. Printing from a cold start often gives me an extra 5 minutes of printing before the extrusion stops. I have tried modifying a number of settings including extruder temp, flow, print speed, etc with no discernable improvements.

Furthermore, I have never seen my secondary fan spinning. Is there any way to test if this fan is functional? Do I need a volt meter to find out if it is getting power? I am unsure how to tell if this is a sensor problem or fan problem.

Any and all advice is much appreciated.