According to your feedback you have not sold for some time! There have been lots of changes in the last few months even and your accoun is no doubt not equiped to sell now.
I suggest you start by going to HELP & CONTACT and enter Start selling, as you will need to provide Bank Details for a start to use Managed Payments. Classic Site is being phased out and may now have gone and you will also have to use the Seller Hub.
