Not allowing my recruit a friend to use their old existing account to link

So my son and his best friend decided to purchase the new expansion and used the link i sent them for the recruit a friend. when they tried to use it for their accounts it would not let them use the existing accounts that they have and play other games on. it wanted them to create new accounts to use the recruit a friend option. I put in a ticket to have this issue fixed but wanted to know if they may have done something wrong or if i did something wrong? is there a special different recruit link for people with old or existing accounts that have not been active? and are you able to fix this issue. they continued to purchase the new expo and their existing accounts and started their subs anyway.

I was given a survey link in game after my ticket was closed and marked resolved. it would not let me submit my survey through so you might want to get that fixed. either way here is what i wrote for a comment in that section. below where you request us to give you feed back.

you should be able to manually adjust some settings like the recruit a friend system for exceptions like my situation. or change the parameters for the time frame a person is gone from the game for previous existing accounts. if a person is gone more then 8 months to a year let’s be honest they are not coming back without incentive. and if you had a shorter time frame for this part of the promotion you might actually see some people that left come back more often. or have friends encourage friends to come back more. also you should give your game masters a path to have escalation requested completed when requested especially with subscribers like myself that have been with the game since its inception.

While I am not satisfied with the complete outcome I understand that the game masters did their very best to assist me.

Thank you