3D printer filament will not load after running the printer out of filament We wanted to test the post process properties of PVA but did not want to print anything.  We unloaded the ABS that was in the printer and then started loading some PVA.  After the PVA was loaded we let it keep going through the loading process until it pushed all the PVA out and we had our test sample.  We then stopped the loading process and started the loading process again to put the ABS back so we could continue with normal printing procedures. Now, the ABS will not load into the right side and started making a clicking/ticking noise.  Our printer is a Flashforge Dreamer.  What is wrong with my printer and how can I fix it?
PVA is nasty filament to print (from experience). I use it in the Ultimaker 3 in a separate designed core (BB) and even with that core the filament frequently cooks up and carbonizes clogging the nozzle resulting in grinding of the filament at the feeder (it also attracts water really easy, so keep it in the bag with desiccant bags).

To clean the inside of the nozzle, a few techniques exist to remove blockage. E.g. by performing a cold pull or using the atomic method. Both techniques rely on the mechanism to insert the (cleaning) filament when it's hot and remove it quickly at a lower temperature. E.g. see here or here. 

The trick is that you pull out all the goo inside the nozzle, you do that by raising the temperature and sticking some (cleaning or high temperature) filament (your ABS will do fine) to the goo. When the temperature lowers, you quickly pull and hope that some of the goo sticks to you cleaning filament. Cut of the tip and repeat until no goo or burnt particles come out and you can push the cleaning filament through the nozzle. You do not need the automatic feeding, it's all manual labor, just raise temperature through the menu and press the lever of the extruder to load the cleaning filament, lower temp and pull back after cooling a bit while pressing the extruder lever.