MetroTalk had some connectivity problems over the past week, due to some new changes deployed by Google Voice. For more details, you can read the following post:
Connectivity issues | MetroTalk
The good news is that the app has now been updated for addressing these. You can get the new version from here:
MetroTalk | Windows Phone Apps+Games Store (United States). Unfortunately, the "MetroTalk Free" version is still pending approval by Microsoft. Please note that although the link provided points to the paid app ("MetroTalk"), you can always download it for free by choosing "try", which gives a version identical to "MetroTalk Free" (i.e. ad-supported).
If you are having issues after updating to the latest version, please try re-installing. If those issues persists, feel free to contact us.
Thanks!