Hi Cheulmen,
You shouldn't trade using all your balance.
Try to open and close a trade with 50% of the balance.

If is still an issue, in the Zorro.ini there is a setting to enable the log.
Set it to 1 (should be already 1 by default).
Then try to run your script and after the error open the log file (BittrexPlugin.log) , clean up your bittrex secret keys and post the log.

Would like to check the quantity sent in both opening and closing the trade.

There are also some changes Bittrex did recently regarding the pip size and minimum amount, that might also create issues.

Cheers
Vincenzo