We noticed another user experienced the same kind of problem, and it is caused by mixing image recording and video recording in one camera.
Foscam cameras support both image and video recording. If a camera uploads both images and video clips, it will confuse the viewer app. Moreover, uploading both images and video clips will require two subscriptions for the camera.
Please also note if your camera is configured with motion triggered recording, and if there is no motion in the scene, then the viewer will have no data to play and hence it will wait. This is normal. We just tested with a few testing cameras and everything is fine.