Hi @trf22
Hope you are doing well, and thanks for posting and for taking the time to test this across devices.
This is a known product limitation in the Adobe Acrobat mobile app: the action button on PDF forms is not currently supported. This is why the button works perfectly on your PC but appears unresponsive on your iPhone. There's nothing wrong with your form setup.
For now, the best workaround for your employees would be to access and submit the form from a desktop or laptop browser using Acrobat on the web at https://adobe.ly/4w6iJN9.
You may also share your feedback with the development team here: https://adobe.ly/4foSKJQ for their consideration and future implementation.
~Amal