I got an email that my eBay balance has automatically been credited to my bank account on 7th October. My eBay balance is now zero, but my bank account does not show the credited amount? How do I get this rectified?

You should check that you have the correct bank account details. If you look in 'payments', you can see the payment was made, when and how much. You can also check that it has gone to the correct bank account. https://ppcapp.ebay.co.uk/myppc/wallet/list