Remotes have an address, so you can use multiple remotes with multiple receivers. The address on your original remote may have been inadvertently changed, and/or the remote off Ebay may have had a different address. These are easily changed.
The other option could be the receiver's RF antenna. Verify that the antenna is still plugged in (wouldn't hurt to unplug and re-plug).
If none of that works, take your remotes to a local store that sells Dish receivers, and try your remotes on theirs. That will determine if it is the remote(s) or your receiver.
Tom
