Possible cause
If clicking the submit button on your form doesn't send the submission, a required field may be set to hidden. Hidden items are not visible on the screen, but the elements themselves still exist.
How to check: Review the Layers panel
Open the Layers panel for your form and check whether any required fields are set to hidden at any breakpoint.
How to check: Use your browser's console log
Open your browser's console log on the live preview or published site.
If there are required fields left empty, an alert like the one below will appear. (Example: The image below shows an alert indicating that the required email field is empty.)
How to fix this
Change the hidden required field to an optional field, or delete the field entirely.
Alternatively, set the required field's box (layer) to always be visible at every breakpoint.