My HRM PRO Plus died after 7 month of use (it shows wrong heart rate, even when not on me still shows data).
After communicating with support it came out that nothing can be done (i lost warranty paper) and no other info can replace it. Not bank transaction screenshots, serial number nor garmin connect data is worth a thing.
No-one ever explained Me what is warranty paper proving that can not be proven any other way.
Just for example my friends wahoo strap died approximately at the same time. All he had to do was sending purchase screenshot, and he recived a new one via warranty (no paper work in this digital era)