Port forwarding CORS not working

I am having trouble with the port forwarding launched from the dashboard:
The app I am using is OpenTripPlanner

Access to fetch at 'https://coder.example.com/api/v2/applications/auth-redirect?redirect_uri=https%3A%2F%2F8080--main--project--ivan.coder.example.com%2F...%2Fgraphql' (redirected from 'https://8080--main--project--ivan.coder.example.com/.../graphql') from origin 'https://8080--main--project--ivan.coder.example.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Access to fetch at 'https://coder.example.com/api/v2/applications/auth-redirect?redirect_uri=https%3A%2F%2F8080--main--project--ivan.coder.example.com%2F...%2Fgraphql' (redirected from 'https://8080--main--project--ivan.coder.example.com/.../graphql') from origin 'https://8080--main--project--ivan.coder.example.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Access to fetch at 'https://coder.example.com/api/v2/applications/auth-redirect?redirect_uri=https%3A%2F%2F8080--main--project--ivan.coder.example.com%2F...%2Fgraphql' (redirected from 'https://8080--main--project--ivan.coder.example.com/.../graphql') from origin 'https://8080--main--project--ivan.coder.example.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Access to fetch at 'https://coder.example.com/api/v2/applications/auth-redirect?redirect_uri=https%3A%2F%2F8080--main--project--ivan.coder.example.com%2F...%2Fgraphql' (redirected from 'https://8080--main--project--ivan.coder.example.com/.../graphql') from origin 'https://8080--main--project--ivan.coder.example.com' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.