Flex Sliderdoesn't display in responsive format, it just disappears

Hello, I have a problem with Flex slider.
It doesn't display in responsive format, it just disappears. It does not generate any errors. On PC it looks fine.
I have tried different solutions but none have been satisfactory.
My url : https://www.tarragonaturisme.cat/ca/
It has been sudden.
Could anyone help me, please?
Thank you