If I fail to pay after my trial ends what happens?

..but you won't be able to use the software if you cancel.

When the trial ends, your plan automatically converts to a 1 year contract until you cancel.  You have 14 days to cancel without a penalty fee.  After 14 days the penalty fee for early cancellation is 50% of remaining months.    See link below for details.

https://www.adobe.com/legal/subscription-terms.html