Don't see Workflow Action Pack App in O365

I would like to try out ‘Workflow Action Pack’ product. However, when I search for ‘Plumsail’, in SP online store, Workflow action pack does not appear. Is it discontinued? What am I doing wrong?

The product is not support installing from APP store, because of permission limitation.

To install it you need download WSP package from the product page and install according to installation instruction.