Early versions of the Polysher manual mention that manual priming is necessary. From customer feedback, Polymaker found that priming wasn't required and now recommend allowing the nebulizer to self prime. Simply fill the reservoir to 90% full and wait between 30 seconds and a minute for the nebulizer to self prime.
If the mist is not filling the chamber or the nebulizer warning light appears, first try pressing the control knob and rotating it clockwise to start a new polishing cycle.