iPhone 11 to iPhone 12 Pro Max Transfer - eSIM Transfer not working

So I am transferring my iPhone 11 data to a new iPhone 12 Pro Max, however the transfer worked, but the eSIM transfer didn't work, and me and my dad tried to call the Support what we're doing wrong, making me transfer my iPhone 12 Pro Max data back to my old phone and my eSIM LTE data plan is still on my iPhone 11, not my new iPhone 12 Pro Max.

Tell me, what are we doing wrong here? Please give me an answer.