Experiencing the same issue. It does work when using a complete redeem code URL (e.g., https://apps.apple.com/redeem?ctx=offercodes&id=YOURAPPID&code=REDEMPTIONCODE) but not when going through the presentCodeRedemptionSheet flow or using a partial redemption URL (e.g., https://apps.apple.com/redeem?ctx=offercodes&id=YOURAPPID).

Experiencing the same issue (See thread -> https://developer.apple.com/forums/thread/708088?login=true&page=1#717403022)