Hi @kimberly87496,
Check the switch using a DMM's (digital multimeter) Ohmmeter function - ''disconnect the power to the device first'' - to ensure that it is electrically working OK and not that it just appears to be mechanically working OK i.e. contacts closed when switch operated 0.00 Ohms on meter, contacts open when switch released OL or infinity reading on meter.
The switch contacts could be welded shut for example, so even though the switch seems to be operating and releasing, the switch contacts may not be.
If the switch is faulty here's the [https://www.hiretech.biz/spare-parts-drawings/htf-orbital-floor-sander-spare-part-images|parts list].
Search online using the switch part number appropriate to your location i.e. household power supply voltage value, to find suppliers that suit you best. Insert ''PSTK'' in front of the part number in the search term.