Editing purge configuration doesn't have options to change the value of the "Enabled" field.
Fixed for revision 776127 in 1.3.3 branch.
It modifies text in the properties and displays a check in the form to allow enable/disable purge configuration.
This also affects 1.3.1.
As a workaround, all purge configurations can be enabled by modifying the database with the following sql statement:
update ABSTRACTPURGECONFIGURATION set ENABLED = 'Y';