Apple Care proof of purchase

I bought an iPad air 3rd gen. a little over a year ago along with apple care+ through apple.com. Paid the premiums and received receipts through email every month. The certificate sent by email says this coverage will continue until I cancel it, which I did NOT do. Always keep insurance for all my devices. Put the serial number in the support site and it says I have no coverage. Called support and they couldn't find anything at all. I'm old and sick and this iPad has been my life during the pandemic. Now it is broke and I'm confused as to why nothing can be done. How do I prove my purchase date if bought online and shipped? Haven't had any claims but need to make one now! Please help me, miss my coloring apps so much and cant afford a new one.