Airtable Forms can't be used within the mobile app... you would need to use a mobile web browser to fill out an Airtable Form.
On a mobile web browser, your prefilled forms should work properly.
However, if you can't get it to work properly on your phone (or even if you can), you can always use Fillout's advanced forms for Airtable, which offers a much better way to update pre-existing Airtable records with a form. No pre-filling is necessary at all, and no automations are required at all.
Hope this helps! If you’d like to hire an expert Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld