My signatory gets the document but is not able to complete the fields, but they can sign?
This is a setup error when the logged in esign user is not selecting "complete" for the signatory role on step 2.
When setting up the signatories the document owner needs to select the function that the signatory will be able to perform on the document - there are two options:
"Complete" allows the signatory to fill in assigned document fields and sign while the "Sign" function only allows them to sign.