For some reason, suddenly the UV quickshade node no longer exists for new files. Files I've already saved have it, and I can even copy and paste quickshade from older files onto new files. I am sure there is some cache or pref file that got corrupted, but I'm not sure which one. I've done first aid on my hard drive, rebooted my computer, deleted and reinstalled the latest daily build and the problem persists.

Well, I tried the usual delete prefs, run first aid, even reinstall OSX without fix. After talking with tech support, I renamed the /Houdini/16.5 and restarted Houdini (which rebuilt the directory). I'm not sure which pref was broken (or plugin), but everything works fine now.

Interesting and weird, I've never had nodes disappear in OS X unless it was some HDA that I installed separately. I guess I would have also tried re-installing Houdini from scratch to see if something went awry along the way. Glad you got it sorted out.

I did a daily build install of Houdini without success. Interesting comment on HDA - I installed DM HDA, tabtoo, and the recent mograph like assets. I wonder if it was one of them. Whatever it was, everything is fine now except the annoying bug where invoking uv flatten from the radial menu crashes Houdini. In network view, it works.

I found the culprit. This is 100% reproducible. It was the houdini.env line for the new MOPS:

MOPS = “/Users/island/Documents/Houdini/MOPS-Master”
HOUDINI_OTLSCAN_PATH = $MOPS/otls;@otls

When that is added, uv quickshade disappears as an option. I initially had a colon rather than semicolon in the second line, but was told by SideFx tech support that for OSX, I needed to change that to a semicolon. Either way, this was the line that lost me the UV quickshade node. Weird.

Weird indeed, I have the same line and my Quickshade node is there and works just fine. The only difference is that I put my MOPS-Master folder in my Houdini preferences folder in my user Library as opposed to in the Documents folder.

Also, I use Colon and not Semi-Colon and it works just fine.

Toadstorm solved it for me (it was a user error). The last line:
HOUDINI_OTLSCAN_PATH = $MOPS/otls;@otls

should have had an extra upslash before the final otls:
HOUDINI_OTLSCAN_PATH = $MOPS/otls;@/otls

Now it works. Still weird.