Do you store your token on Bittrex on 22 June 2020? If so, your token is already automatically swapped into a new one, DAWN. Check the balance on your Bittrex account, if it is empty, then you didn't hold it over that period of time or there might be some issues about the swap.
For full information, take a look at
Bittrex Global supports Dawn token swaps.
Thank you for your answer. This is exactly what I thougth had happened but it was not the case. My Bittrex 1ST balance was the same that back in 2017 and my DAWN balance was zero. I think that some action was required in Bittrex to claim the swap 1ST to DAWN that was performed the 22nd June 2020.