Ensuring a stable internet connection should be your first point of call.
For all other issues restarting your device often solves these.
Do this by:
Holding down the power button,
Waiting for the machine to turn off and then,
Turning it back on.
In some instances a hard reset may be required
This involves:
Turning the device off,
Removing the battery from the back of the device,
Waiting 3 seconds and then,
Reinserting the battery & turning the machine on
If the above does not work we suggest searching for specific troubleshooting guidance in our Help Centre.