Loosing coins

Can anyone help me understand why I'm loosing coins please   Three times now, when I come to the end of the day to bank my coins, unlike most nights when I simple have to keep pressing the coin chest to start the process of banking, It asks me to sign in using options of Facebook, google etc. when I press any of them, it takes me to the usual coin chest page BUT THERE ARE ZERO COINS, even though I've done well over 10,000 steps. It just seems as though they get deleted! It's only just started happening but so disappointing. Does anyone know why I'm being asked to sign in when it's obvious I am already registered. Thanks