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Try turning Off the printer for 1/2 hour. See if that clears the error.
While it is Off, remove the tray, and re-seat the tray.
Try putting one sheet of paper at least, in all trays, and in the manual feed area also, if your printer model has a manual feed. Provision all paper sources, in short, with some paper in each.
If the 'load paper' message is owing to the print job being mistakenly directed to the wrong tray, or to an unexpected and unintended paper source, then that paper source will react by feeding in paper in that area. That, if you see that happening, will provide a clue as to which paper source the print job is being directed to. With that data, the setting may be corrected.
Or, you could check the Paper Source and/or Paper Tray setting in or on:
1. the printer's own settings
2. the printer's driver settings on the computer, and
3. the printing settings in the program you are printing from (if it has such settings. On Windows, a way of testing this more easily, is to print from Notepad, which has no printing settings of its own, eliminating (3) from the possible causes of the error message.