It’s fairly common from my experience that a turntable that hasn’t run for a decade or more can have enough dried lubrication and even enough slight corrosion (oxidation) that it can bind up the movement pretty tight. Usually, I remove the turntable from the console and gently and sparingly wash the underside cams and levers with a degreaser like Varsol, WD40 or similar and I’ve even used gas very sparingly until everything starts to move again. But, be very gentle, you can easily bend the cams and plates if you get too aggressive. I’ve found the best way is to manually operate the turntable after washing everything with the degreaser is by selecting play, then gently rotating the turntable until it starts to function again. The ideal is to be able to get the full function of reject manually from start to reset. If the turntable won’t budge there can be corrosion between the center spindle and the turntable as well. Once everything functions again manually, relubricate the works. Vaseline or a light grease is good for the main cam and a light oil like 3-in-1 or sewing machine oil for everything else. Also, you may find the drive tire is hard or has flat spots and will need to be replaced. There are sources for new online. Cartridges and needles can be found on eBay.
Good luck John