I'm not familiar with your printer, but I work with large format machines.
First off, It's important not to force the print carriage (the part that holds the print heads) as this could damage the belt that attaches to the motor or the motor itself.
As a first step, you can always turn both the printer and the computer all the way off and then back on. While the printer is off, unplug it and hold the power button for about 10 seconds. Not sure if it matters but I turn on the computer first, then the printer. That way I can make sure there is nothing in the print queue.
If that doesn't work, The manuals usually have troubleshooting for this kind of problem in the back section. There is usually something like a maintenance cartridge or other device that is keeping the motor engaged and will keep the print heads from being moved.