Why does EchoSign receive blank document, even though I have filled in all fields?

I have been given a timesheet pdf to fill in.

It contains the option to send to someone for signing.

It does not allow me to save the form after I have filled it in.

I fill in all the fields, then I click Sign, and it says it is uploading the pdf. Then I am taken to Adobe EchoSign in my browser.

I fill in the email address, but when I click Preview, the form is empty.

If I go ahead and send it anyway, a blank form is sent to the recipient.

None of the data I entered has been saved.

Am I doing something wrong?