Try lowering the lever just past the vertical position and letting it drop on its own with the platform and arm. This usually works; please give it a try and let us know if it resolves your problem. If not the mechanism may need to be replaced or rebuilt.
rega rb300 tonearm lift not working - fixable
the tonearm lift no longer lowers my rega arm. I've had the arm quite a while. is there something in there that may have dried out, anything I can do to bring it back to working condition?