Nope. Works fine for me. I’m also using 64 Bit Reaper and SD3.
Check you’ve installed the latest SD3 updates using product manager, then check you have Reaper pointing at the right location for the VSTi.
Oh and whilst your at it, load an empty Reaper project and just load SD3.
(There are no issue here with either so it’s another VST or your setup
)