It takes time to for contents from a mobile device to start playback via the home network.
Depending on the usage environment, playback may take some time.
The following operations may improve the situation:
Confirm whether the Wi-Fi connection from the wireless router is strong enough. Put the router (or access point) as close as possible to the TV. However, keep 1 m of separation.
If there are multiple wireless routers (or access points) in the area, signal conflict may be occurring. Try stopping any unnecessary wireless routers (or access points).