Problems with IntelliSense code snippets are typically caused by two problems: a corrupt snippet file or bad content in the snippet file.
You may be missing a project reference. Examine the documentation about the snippet. If the reference is not found on the computer, you will need to install it. Inserting a snippet should add to the project any references needed. If the snippet is missing the reference information, that can be reported to the snippet creator as an error.
A variable may be undefined. Undefined variables in a snippet should be highlighted. If not, that can be reported to the snippet creator as an error.