Your offer link in kintura should be something like this : i highlighted the token to be changed.
https://zzzh=waWQiOjEwMzE2NjAsInNpZCI6MTA0MzM0Niwid2lkIjo3OTczMSwic3JjIjoyfQ==eyJ&click_id={cid}&cpa_cost={cpa_cost}&si1=&si2=
Your postback should be like this:
Paste it to Evadav widget screen...