We have a Prusa i3 MK2 and we've changed for a print with another colour material but when I pressed "load filament", it didn't make anything.
Often after five times doing that the printer works. I don't have any pictures but the filament is in the hole and the printer holds it. However, it doesn't push it into the extruder and the remains of the old filament do not come out, so I wonder why the motors just stop and don't work.
Sometimes there are no problems - sometimes more and sometimes less. I hope someone has the reason for this problem.
First make sure that the hotend is hot enough. Second you need to check your extruder if it is clean. Third try to push the filament by hand and look if it comes out. If yes than the problem should be in the motor. The motor connection wire could be loose.