Does it print anyway? I sometimes have messages like that and it doesn't matter.
Try to get your paper sizes matched in your printer's settings and in LC in Options - Current Drawing Preferences - Paper.
Maybe not the fault of LC. Maybe there is Print to File ticked in the printer driver's dialog. I'm not sure, but I think this can happen when you have accidentally tried to print to an offline printer before.
Try using a different paper tray/feed with your printer.
Does it really print from other programs?
Or layer set to not printable in the layer list, printer symbol greyed out.
No other ideas, sorry.