Dear Rose,
Thank you for your help.
We tried everything step by step you proposed.
Installing storefront we get a positive result, but despite updating the xstore theme, and deactivating any third party plugin that is not in the list of xstore compatible plugins, unfortuentely there is no progress with the xstore theme. Please let us know if we can try anything different.
We left you a temporary access in the last mail, it would be great if you could have a look on it.
Thank you very much!
Best regards,
Tiffany