it's normally friend, i get it too...
this feature released arround 6month ago, before it i can see any deposit history and trade history from my bittrex account
That's weird. Why would they delete history, I have an account there but haven't logged on in a while since I don't trade alts anymore but will check if they have cleared my history as well. OP have you asked the support about this?
I guess new trades would show in my account's history, but like you I hadn't logged in since last Easter and haven't traded there since then. Support seems the only option for getting my history back. They might have deleted it because my account was inactive for so long, but it's weird.