Theme Update issues with Piano >>>URGENT

All modification and custom CSS seems to have disappeared and I am unable to get in to the 'customise' editor to see if any of it is still there and able to be re applied to the content.
Is there anyway to 'roll back' the update and/or access the edit facility?

Please look at this as a matter of urgency and I have also authorised support access, should it be required.

Thank you

AJ