I haven't used Melodyne since SPLAT and now that I'm on CbB, I noticed it doesn't appear under Region FX. I found a post that mentioned adding it via Bandlab Assistant, so I went and did that. Is there an extra step involved to get CbB to recognize it as a Region FX?
After verifying the vst3 plug-in is physically on the disk, the default path is "C:\Program Files\Common Files\VST3\Celemony\Melodyne", run a VST Reset from preferences with "Scan in Sandbox" and "Generate Scan Log" enabled.
Then if the plug-in does not show up, there is a scan log to review.