If you have issues with filament not being grabbed by the gear then you might want to check that you have placed the spring mechanism correctly
If you don't place all parts correctly, it will not create enough pressure on the filament for the filament to be pushed through.
Make sure you are not missing a part:
You should either have a silicone ring or two metal rings as well as the white block, metal cylinder and spring. See photos below.
The silicone ring should be inserted into the white block before the spring. See photo below.
The metal cylinder should be placed standing up (vertically) and not horizontally.