1. VST3 is not supported. The older 64-bit VST dlls are supported, however.
2. Nested folders. Make sure the dll files are not nested too deep in folders. For example, MeldaProduction creates extra folders named Delays, Time, Reverb, etc. & installs the dlls there, but they will be invisible to RX 7 unless you move them up one level.
3. Make sure the actual path to your VSTs is specified in the preferences panel & rescan.