What happens if my purchase date is not validated?

this means that apple doesn't know where or when you bought your device if you bought this from eBay this may show that the device is fake basically its not listed on apple's "system" although you can call apple support to confirm that https://support.apple.com/en-us/HT201232

The purchase date is used to confirm warranty coverage.

https://support.apple.com/en-us/HT202741

yeah but it says its not validated it means that apple doesn't know when this device is purchased therefore no warranty coverage, if you check your device even if your warranty has expired it will say purchase day valid

Apparently when there is no more warranty on your device, Apple will not go above & beyond to help you with your device. Tech at Genius Bar initially offered to send Apple Watch for possible software issue at no charge then realized device had no warranty coverage left. So much for standing behind your product.