Problem with the billing / delivery address at checkout

Hello,
After the most recent update I found that I have a problem with the billing / delivery address at checkout. The option to calculate the delivery fee has appeared on the cart page. I haven’t used it before.

If I disable it from the settings, the shipping fee does not appear on the checkout page when I enter the address and I receive the error “No delivery option is available. Please make sure your address was entered correctly or contact us if you need Help”

If I leave the delivery fee calculation activated on the cart page and fill in the same error only on the checkout page. You must select the country, region and city from the cart page to update on the checkout page and the customer can place the order.

I tried several options, to disable the possibility to select the region from checkout, not to calculate the fee, etc., but without success.

Please help me with this situation. We do not need this option to calculate the shipping fee. We have a fixed shipping fee regardless of which product is purchased and free shipping over a certain order value.

Things would be simple … but this error seems to complicate matters.I use the Customizr theme.

Thank you in advance!