New M1 Macbook Pro, warranty expired
A call to Apple support or web interaction would let you provide purchase information to correct an accounting error on the registration. This has been true for a decade and isn’t specific to the M1 Mac.
To get to this, open the “About this Mac” item from the Apple menu or use this handy web site - https://support.apple.com/repair-products

Select the service tab and then the check my coverage status. Apple doesn’t need you to provide anything but a receipt that you obtained from your seller in most cases.
Also keep in mind, sales into some countries mean you have to provide proof of purchase or seek support first from the person you bought the product or a company in the region of first sale instead of Apple directly.

https://www.apple.com/legal/
https://www.apple.com/legal/warranty/statutoryrights.html

Hopefully you didn’t buy a Mac that didn’t even finish manufacturing by Apple or was stolen directly from Apple. I clearly can’t know what information an Apple agent would find in their research to decline coverage. There are so many edge cases you may not have considered that someone at Apple not only has faced multiple times, but had to write a playbook for how to handle these rare cases so they’re being consistent and not “shooting from the hip” call by call. One might be if you had a Mac they used in store for a display and it was stolen during a robbery. I could understand the call asking for support on those Macs to be a short one and read from a script that is designed to bring the call to a quick conclusion.