Salesforce have announced the retirement of Workflows and Process Builder.
Organisations with Workflows/Process Builders will still be able to use and edit these for a little while, but cannot add new ones.
Payments2Us will migrate Workflows to Flows over the coming releases. Keep an eye out on this FAQ for updates.
NOTE: You cannot use the migration wizard to migrate the standard Payments2Us Managed Package Items. We need to do this as part of a release update.