the choice to autofill or not doesn’t appear.

Even though I have ENABLED continue forms later, the choice to autofill or not doesn’t appear.

Hello Lisa, Could you please let us know which form you refer to so we checked? We will wait for your reply. 

https://form.jotform.com/90445411384151
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I have tested your form and it seems to save answers correctly. Please note that autofill on forms works the following way: when user has entered some values, those answers are saved into browser's local cache for 24hours. So, when user loads the form via same browser again (or reloads the page) answers are filled to the form automatically. Here is a screencast, I have reloaded the page to check autofill:

Hej, is it possible in this case to for longer cookies periods of time from default 24 hours to some day, like 30 days or so ? 

There is different option to save form progress in user's session, it will save the data for 30 days. Here is a guide for forms with Classic layout: How-to-Save-Forms-and-Continue-Later

And for Card forms: Setting-up-the-Continue-Forms-Later-Feature-in-Card-Forms