Leave opening balance & monthly earned leave

I am using V13.x.x.x version of ERPNext. I am newly introducing ERP for all my employees so I want to carry forward previous leaves (leave type is Earned Leave). I manually allocated un used leaves for the year 01-01-2020 - 31-12-2020 (last year) and for this year added leave policy. However I am still not able to carry forward the leaves to this year. I even set the expire carry forward leaves to 365 days. But still no luck. Can ERPNExt experts suggest?
Leave Balance -