Pre - Plex 7.2.1 uses Visual Studio 2005 and the corresponding Crystal Report (CR) is version 10, 11, or 12. VS 2013 will use CR 13.0.9.
https://apps.support.sap.com/sap/support/knowledge/public/en/1514084
Here are the steps used to change a pre-7.2.1 model with Crystal Reports to a 7.2.1 model.
1. Uninstall the Crystal Report 10, 11, or 12.
2. Install Crystal Report 13.0.9.
3. Find the source Panel that contains the Crystal Report, in case there are several sub-Panels that inherit the source Panel, so hopefully only one Panel change is needed. In the source Panel, "rename" and set "Exist to No" for the existing Crystal Report (CR) hosted on panel. Add CR v13 control with same name as the original. This is done so any possible references in the Action Diagram and all other places will continue to work. So, the original CR is still there, just renamed and hidden, with a new CR in its place.
Here are a few of the screenshots from environment.
<Please see attached file for image>

Location of control: Picked up from ActiveX control properties from Plex panel.
C:\Program Files (x86)\SAP BusinessObjects\Crystal Reports for .NET Framework 4.0\Common\Crystal Reports 2011\crystalreportviewers\ActiveXControls\CRViewer.dll
Crystal report v13 listed:
<Please see attached file for image>

We can rename (and set Exist to No) existing Crystal Report (CR) hosted on panel and add CR v13 control with same name as older one, so all the references works as is with Action Diagram and all other places.
<Please see attached file for image>