If you create an account on Tidex.com and transfer Steem to your Steemit wallet on Tidex, you will notice that the Steem never arrives.

If you look at the Tidex Steemit account @tidex you will see your transaction appear there. You will also notice that for over 2 months users have been depositing Steem to Tidex and no one has received it. Tidex quit transferring Steem over 2 months ago.

If you attempt to contact them directly, good luck with that. They don't care to respond.