I don’t see any of my previous messages when I log into my DSM mailbox.

Your DSM mailbox might be having difficulty opening if you have a slow internet speed and the server times out before all the messages load.  Try again when you have a faster internet speed.

If you have alot of messages in your folders the server may time out before all the messages can load. Make sure you also routinely clear out old messages and remember to delete messages from your trash folder too.