Thats too bad, looks like you need to amend 2018 (refunds are gone for 2018) and see if anything is left to carryover to 2019, then amend 2019 (still time for a 2019 refund to be issued). Thats a big chunk of credit to lose.
♪♫•*¨*•.¸¸♥Lisa♥¸¸.•*¨*•♫♪
