As Mitchel says, this is indeed due to a security restriction in iOS. However, you can tell iOS to allow external content to be loaded into your application by adding the following tag to your phonegap config.xml file and then rebuild your phonegap application:
<!-- Don't block any requests --> <access origin="*" /> <!-- Allow links to sprintr.home.mendix.com --> <allow-navigation href="https://sprintr.home.mendix.com/*" />
This will allow the Cordova browser to navigate to, and load, content from the sprintr portal.
You can find more information about these configuration options here: https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-whitelist/#navigation-whitelist
The feedback widget loads an iframe in a popup, unfortunately iOS for security reasons doesn't like iframes from external sources. For as far as a I know there is no work around you can provide for this as it requires a server sided configuration change on the Sptintr server. We encountered this with a Mx cloud hosted app, something Mx never resolved. You could try sending in a support ticket but I wouldn't expect to much from it.