"Can you try opening Options>Rhino Options>Plugins and seeing if the Neon plugin is checked as loaded? If it's not, click the 'Enabled' check box and restart Rhino. Let me know if that works please. "
"Thanks for the reply.
Repair didn't work. Error now says "Blocking plug-in Neon 1.0."
Version 5 SR3 (5.3.30426.17065, 4/26/2013)
Neon installer is the most recent, downloaded two days ago.
Thanks!"
"Try running the Neon installer again with the 'repair' option. Have Rhino closed when doing this and if it doesn't work, let us know the Rhino 5 version you're running please as well as the Neon installer version. "