As it seems, I'm having the same issue as hundred of other users. I was unable to cancel my Adobe Stock account as there is simply no button for cancelling. I had the free trial, deemed it not worthy to continue, and don't want it anymore.
Please cancel my account - thanks very much.
Please contact support through call/chat for the cancellation requests:
**Be sure to remain signed in with your Adobe ID before accessing the link above**
In case you are unable to reach support through the above-mentioned link please see Contact Support FAQ: Unable to reach support through the "Contact US" link
Feel free to update this thread in case of any additional query.