[{"InvNo":"ISD220311","InvDt":"30/04/2022"}]
Error " [{"Code":"VALD0011","Message":"'Reference Document Number' and 'Reference Document Date' does not exist!
Above error comes when entered document number or document date is incorrect either not available in portal. to solve this enter correct document and sync the data from GST.

Notes
There is one setting under Import "Import Documents without Reference:" if this is disabled then user does not need to put the reference preceding details but in ISDCN system will ask to put the details mandatory.