Posted a reply to Getting Card Expiration Date Is Invalid on Checkout Page, on the site WordPress.org Forums:
I encountered this exact issue with WooCommerce 5.4.0, updating to 5.4.1 resolved it for me.

Posted a reply to Expiration not valid error, on the site WordPress.org Forums:
I'll echo @abuzon — I was experiencing the exact same issue with 5.4.0 and updating…

Posted a reply to Expiration Date Error on CC Checkout 5.4.0, on the site WordPress.org Forums:
I was having the exact same issue using WooCommerce 5.4.0 & Authorize.net in both test…