Based on the attached pic. ( Filemaker Support White Page ) I get the "Prev" and "Next" buttons at the lower left of the display on the iPad Mini not the signature button when I navigate and I tap on the signature container field.
When I click on fields other than my signature field and then click the "Next" button, and click "Next" into the signature fields, there is a area where the key board use to be for the previous fields ( text ) that is now blank but I'm not able to enter a signature with my finger. Only the "Prev" and "Next" buttons remain ?? Strange.