Quick Start fail

Hello,

I am trying to move from my old iPhone 8 to my new iPhone 12 mini but the Quick Start option for data transfer is not working. After I've selected certain options and data transfer is about to commence, it gives a message saying that data transfer was cancelled and the phone needs to be restored to factory settings. After trying everything (both phones were charging, had wifi etc) and failing, I tried to backup through iCloud, however my old phone wasn't recently updated (due to lack of storage, so I upgraded the storage on iCloud), but I cannot manually back it up, neither through phone nor my Mac (there is some error where it stops on its own). Do I wait for the old phone to manually backup during the night and hope the next day I can backup my new phone up to date. Or maybe can I update it now (with the old backup from a year ago) and then update it when the old phone backs up?