Activation lock need help

Hi

I’m desperately looking for some help. I purchased a refurbished MacBook Air 2020 model from a uk store. No sure if I’m allowed to name.

This was a present for my 13 year old son. On Christmas day he set it up without me knowing and made an iCloud account for it but did not put the correct dob. The next day he informs me he’s locked out of the MacBook because he entered the wrong password

I was assuming to both the Mac and iCloud. There’s no way to recover the iCloud due to not knowing the dob. He has learning difficulties and didn’t think it mattered was just excited to get on it. I contacted Apple who have asked for proof of purchase. I’ve sent all proof I have including sales receipt, packing slip, bank details showing payment but there not accepting it.

The company bought from won’t help saying because I bought it unlocked and my son locked it basically tough luck. I paid £1014 for it actually dearer than Apple but I believed this store to be an official Mac reseller due to the fact it claims to be the UK’s biggest seller of new and refurbished Apple products.

Does It sound right that a legit store can sell you a refurbished Mac at retail price but don’t have to offer any help in relation to activation lock.