If you are using the XenDesktop Connector Tech Preview, uninstall it and then install Citrix Connector 7.5. Citrix Connector does not upgrade the XenDesktop Connector Tech Preview.
You can use XenApp 6.5 Connector (SP2) side-by-side with Citrix Connector 7.5. The XenApp 6.5 Connector deployment handler is the only XenApp 6.5 Connector component that you can upgrade to the Connector 7.5 version. You can use the Connector 7.5 deployment handler for both XenApp 6.5 and XenApp or XenDesktop 7.6 or 7.5 deployments.