eBay can suspend your account for a number of reasons provided in their user agreement policies. If your account has been suspended immediately after creating it or buying an item then it may be issues related to your billing information, incorrect profile information, duplicate accounts, IP, or WiFi.
If you are sharing an IP addresses or Wi-Fi with users whose accounts have previously been involved in any form of fraud or scam activity as defined in their policies, then your account can also be suspended. Such suspensions are atomically made by bots and you are not likely to have your account reinstated.
If you are using a VPN or remote virtual desktop that is being abused by scammers, then the system can also flag your account as being hacked. In such, a case, your account will be reinstated after some period or you can contact support.
eBay has provided details on how to have your account reinstated on this page. You can also log in to your account and request a call back (US) or UK.
If the only available contact option in your location is email and you are only receiving automated replies, then you can contact eBay support through Facebook @eBay or Twitter @askebay