Card blocked

Tried to use my card on Saturday and it kept declining whilst I have funds available. Checked on the Nedbank app and it indicated 'Requires approval'. Dont know what it means. When I contacted the call centre, I spent 16 minutes waiting to be assisted. When I was eventually assited, the agent could not tell me why my card was not working and said it shoulf work now. Tried to use the card today and it still declines.