Take a look at the release notes, drop down relationship - as currently implemented in previous versions, is not the same. You need to create an action in vRO and reference that in the properties of the drop down list.
<From the release notes>
In vRealize Automation 7.0, the property definitions no longer use the attributes. You must recreate the property definition or configure the property definition to use a vRealize Orchestrator script action rather than the embedded control types or attributes.
Workaround: Migrate the control type or attributes to vRealize Automation 7.0 using a script action.
- In vRealize Orchestrator, create a script action that returns the property values. The action must return a simple type. For example, return strings, integers, or other supported types. The action can take the other properties on which it depends as an input parameter. For information about creating script actions, see the vRealize Orchestrator documentation.
- In vRealize Automation, configure the product definition.
- a. Select Administration > Property Dictionary > Property Definitions
b. Select the property definition and click Edit
c. From the the Display advice drop-down menu, select Dropdown
d. From the Values drop-down menu, select External Values
e. Select the script action.
f. Click OK
g. Configure the Input Parameters that are included in the script action. To preserve the existing relationship, bind the parameter to the other property.
h. Click OK
