Adobe Acrobat Reader DC is a free software and has access to limited features.
You will not be able to use the "Prepare form" tool in this application.
Prepare form tool can only be used in Adobe Acrobat DC application.
I have checked that you have recently canceled the subscription.
Let us know if you have any questions or need any help.
I was also having the same issue but had NOT cancelled the subscription. I had to "search" for prepare tool and then was able to accomplish my task.