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Your form's submit button will be disabled until valid data is entered into all required fields and if data is entered into an optional field that data also must be valid. You will want to test your form to verify that all the fields that you want to require the user to fill are indeed set to required in the form. If the user does not enter data into all your form's required fields the submit button will remain greyed out until they do. This prevents the user from submitting a form that does not yet have all the data that you require. The submit button will also disabled if you enter invalid data into an optional field. For example enter abcde into a Money control. An error will appear to alert the user that the entered data is invalid. And even if all required form fields are filled you'll see that the submit button is again greyed out until the error is corrected. For example, replace abcde with 89.25 and the submit button can be clicked.
If you click on the Submit button in a form that contains invalid data or required fields that are empty ( Submit button is greyed out), the message shown below will display. This alert is very helpful to users when trying to determine why a form does not submit.
Sometimes you'll test your form and see that the submit button remain grey'd out even when all required fields appear to be filled with valid data. The cause is always a hidden required field with no data or a hidden field with invalid data. Since the field is hidden your users won't be able to enter a value into that required field nor to correct an invalid value in that field and will therefore never be able to submit your form. In a simple form it won't be hard for you to open it in the form designer, find the hidden required field and fix the problem. In a large form or one that has dynamic business logic that makes fields hidden/visible or required/optional or sets values in business rules, you'll need to debug this problem while testing the form.
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