RTO India — GETTING MESSAGE "YOU HAVE ALREADY APPLIED FOR DL"

I applied for dl for my son, after 1.5 month of issue of ll on sarthi.Parivahan.Gov.In site.
On entering ll number and dob, i got message that
"you have already applied for dl"
it doesnt allow me to proceed further to apply for dl.
Details are as under -

ll no: gj06 /0049408/2020
dob: 22.09.2004

kindly resolve the issue so as to apply for dl within time frame of 24.05.2021.