Problem encounter when linking evisa

[mtwtfss]

Hi, my friend granted leave to remain in February. He only received the decision letter from Home Office and they did not issue him a BRP as home office has phased out BRP.

He created account on UKVI and the question about his reference number, so we put down the home office reference number from the decision letter we received from Home Office. However, it shows that application could not be found.

Anybody encounter the same problem and how do you all solve it?

Thanks