27" 2020 Imac ram upgrade

Came with 8 (two 4's) & got 2 two OWC 32's to upgrade to 64. The pc will not start.

I tried every combination possible & still no joy. The only way it will start is with the original cards, either in slot 1&3 or 2&4. Any combination including the new 32 cards will not work. Even just the new cards alone in original slots. Read numerous forums on the process & their problems.

OWC was supposed to be the most reliable.

Am I missing something or did I get bad cards?