Below is from application guide :
Note: Your application will be returned to you if it is:
- not signed and dated
- dated more than 90 days before we receive it
- post-dated (dated into the future)
- make sure that the date of signature on the application and the date on the physical presence calculator printout are the same
You should make sure that your application is not
dated more than 90 days before they receive it. If IRCC specifically mentioned resending the same application just add missing docs then resend it if they did not, take note of the above before you send it back.