Resolve Google Auth Callback Issue

I'm encountering a "Cannot GET /auth/google/callback" error in my MERN stack application. The issue seems to be rooted in the backend (Node/Express).

Details:
- The authentication mechanism employed is JWT (JSON Web Token) with Google.
- The callback route handler has been implemented and is in place.

I am looking for a professional with strong expertise in Node.js and Express, who can troubleshoot and resolve this issue promptly.