How to troubleshoot when the generator won't complete the schema generation

[MincePie]

I am trying to add a logout mutation to my user resolver. All of the other mutations in the resolver have generated the schema.

@Mutation(() => Boolean)
        logout(@Ctx() { req, res }: MyContext) {
          return new Promise((resolve) =>
            req.session.destroy((err) => {
              res.clearCookie(COOKIE_NAME);
              if (err) {
                console.log(err);
                resolve(false);
                return;
              }
      
              resolve(true);
            })
          );
        }

When I run the script to generate the schema with the additional logout mutation, I get an error that says:

AggregateError: GraphQL Document Validation failed with 1 errors;
Error 0: GraphQLDocumentError: Cannot query field "logout" on type "Mutation".

I am looking for sources that I can investigate for what I can do to get the generator to run. Any suggestions would be gratefully received.

Thank you