Trying to transfer ownership of a pet

Please help me I want to get my cat back.
I had to get a new account and so now my pet isn't mine :(
But I am opped so if there's a command I can use to fix this that'd be amazing. I tried 
/data merge entity cf32f809-598d-4329-b38b-49715d596490 {Owner: [[I; my uuid]]}
And it said Modified entity data of cat
But it didn't actually do anything