Thank you for reply, in extention manager, LibFredo is active, and also the Curviloft is latest version, but it still cannot run curviloft,

I have installed the LibFredo6 ver 7.7 and Curviloft. After I restart the sketchup, Warning message said that I must use LibFredo6 ver 6.9 or after.
But in Plugins Manager it did show Fredo_6 Curviloft loaded.

Anyone can help in how to run the Curviloft