Are you using Checkout Fields plugin? Try deactivating it and then activating it back, after that check if default fields appear on the Checkout page, as they must be there for sure. If the issue persists, submit a request to our Help Desk, so we take a closer look at the issue.
I solved the issue after support suggested I contact WPML. I didn’t need to contact them since support gave me an isea of the issue. I made a video in case it hels someone else Video here