It seems that I found a solution!
Had the same problem on a client site, Elementor is installed, but not used in this case.
Somehow a flex element is hidden there between the 2 columns, so if you hide that with CSS, it works again!
The code you need to add to the custom CSS:
wc-order-attribution-inputs {
display:none;
}
Woocommerce > Settings > Advanced > Features. Option for “Order Attribution” which is enabled.
This adds a “wc-order-attribution-inputs” tag inside the checkout form causing the flexbox to break into 1 column.
Greetings,
Mark
