Having the same problem (on an LG G3). Is there a timetable for this issue being resolved? My building does not permit sprint network connection, so WiFi calling is essential.
At this point this issue is clearly not rooted in any of our wifi networks, nor our individual handsets. This is a sprint network issue that has corrupted the functioning of WFC. We don't need anymore waste of time instructions of reset this, reboot that, toggle this etc.
What help will the store be, if the issue is not the phone (unless the case is the unlikely event that a large number of people in disparate locations with different devices simultaneously begin experiencing the same device-caused problem)?