Posted in the last Pre, but Orchestral Tools Sine Player vst3 isn't showing in REAPER. It does in Studio One for example.
Local plugin paths are all fine and have done a full re-scan to no avail. The location (default install) is,
"C:\Program Files\Common Files\VST3\SINE Player.vst3\Contents\x86_64-win\SINE Player.vst3"
Download link for the Sine Player,
https://www.orchestraltools.com/store/get-sine