Working form now suddenly broken- (mismatch data type ...)

Working form now suddenly broken- (mismatch data type ...)

A form that has been working for over a year is now showing this error:

Mismatch data type for function days360 at argument index 2 expected data type [TIMESTAMP] found dataType STRING Line:(1)

Do I need to rewrite my app or is this an error on Zoho's end?