If I change the status of an inactive pet or client to active within the PiMS, can I add a plan that same day?

Yes.
Click the Quick Sync   icon within the Petly Plans application to update the database before performing a search for the pet or client. Perform a search after 7 minutes.

If the pet or client still does not display, have an administrator perform a full sync by placing the mouse pointer over the Menu and selecting Admin > Syncs & Automation. The administrator must then click the Sync Clients link to import the latest client information and then the Sync Pets link to import the latest pet information. Once the full syncs are successful, perform another search for the client or pet.