I have two annoying little problems when it comes to Melodyne. The first is that it doesn't show up in the Region FX menu in track view. The second is that, once Melodyne is applied to a region, I cannot remove it using the button in the corner of the clip. For that matter, I can't remove it at all, except by using "undo." Has anyone else experienced this?
 
EDIT: I'm on X3a. I just got X3 today, and for some reason, it's not working for me to download X3b.

@ your first problem: you need to have melodyne installed as VST3. Check the default list of your plugins and see if it is listed as VST3. 
 
If you have it installed as VST3 but it is not showing in the VST3 list, then you need to revisit your VST path settings. I actually had to add the sub-directory in which Melodyne VST3 resides to the scan path so that it was recognized (this is X3b)

Melodyne appears in the normal plug-in menu under the "VST3" subdivision, but does not appear in the Region FX menu. I was finally able to get X3b to download and I installed it, but that didn't fix anything.

I had the same problem, and a vst re-scan solved this matter! I hope it will help you too.

and here is the link to my previous thread:
 
http://forum.cakewalk.com...RegionFX-m2909533.aspx

That did it! Thank you!! I reinstalled to try to fix this problem and it's funny that, somehow, the reinstallation didn't force a rescan.

FYI
 
Depite having it fixed in X3b Melodyne went missing again from the Region FX in X3c.
 
So I tried the usual rescan and although it was listed in those new fancy blue pop-ups that melodyne vst3 is being scanned, it never appeared in my region FX.
 
So I reinstalled, re-scanned, nothing, reboot, reinstalled, re-scanned, still nothing ... WTF ...
 
Then for some reason I started the scan from "Utilities/Cakewalk Plug-in Manager" rather than "Preferences/VST settings" and it worked. Melodyne is back.
 
Very strange. I had always thought that it should be calling identical code under the hood.