As you use Robert's feeder design you are able to manually push filament into the Bowden tube and through the heated hotend. I would set the hotend to something like 230°C and check if you can easily push the filament through. If you can, then it's rather a problem of the feeder, if not, then you can check at which position of the filament in the Bowden tube resistance starts.
After you replaced the Bowden tube, did the troubles start immediately again or just after changing filament? If the latter is the case you may check the Bowden for very tiny strands (really hardly visible). They happen when the standard filament exchange routine is used (due to the still hot filament while pulling out). Since I installed Robert's feeder I only use the atomic method to remove the filament and the 'insert material' option in the maintenance menu for the new filament.