What exactly is happening, are you getting an error code, is it saying user name password don't match or does it just not log in? Firstly make sure you are using your Sky ID as user name not email. Also remember passwords are case sensitive and mobile keyboards can be a pain. If you are sure both are correct then check app is to date. If not try updating. If it is try uninstalling and reinstalling.
If still not working speak to technical team via chat.
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