When I got my Ender 3 in and had print issues (like it was under extruding), I finally discovered that my hot end had over 2mm gap between the throat-screw and the hotend. I ordered a new new hotend but while I’m waiting on the rowboat from China, I broke down the hotend and fixed the issue.
I’m offering this idea because it sounds like you ordered your Ender 3 like I did in July. The issue was maddening because nothing seemed to print right.
Here is a picture of the filament that was left in the hotend tip after I did a cool pull to clean out the material. Taking the tip off showed this huge chuck of material left. This may or may not apply, but check the setup of the hotend to make sure the tip is flush with the throat screw on the extruder.
