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Force quit the frozen or printing screen and see if it works or not. Press Command, Option and Esc keys and this will bring Force Quit. Select the printer window there and click Force Quit. Then try to print again.
If that didn't work, then turn off the printer and unplug it for 2 minutes. Then plug it back, turn it on and try printing.
If that didn't work, then we can reset your printing system and see if it works or not.
After resetting,your Printer will disappear from the list. Click the + button in there (in left corner) and add it back
Please let me know if that didn't work, so we can continue troubleshooting.