Question: I have 2 radio button under a group box and i made first one group as true. but when i am adding radio button variable the it showing message "Failed to return new code element possibly a syntax error", what would be the reason?

Answer: 
Delete the Class Wizard file (.clw) and the Intellisense file (.ncb) file from your solution directory and try again.
I meet this issue on VS 2022. I solved it by these steps:

1. closing VS solution.
2. delete .vs directory
3. re-open \*.sln