Not unless your creditor claim was discharged by the bankruptcy court in 2017.
You can only claim the loss in the year you had the loss. If the company went bankrupt in 2006, you could have claimed the loss on your taxes that year. If you were a creditor in the bankruptcy case, and waiting to see if you would recover a portion of your investment, you can claim in the year the US Bankruptcy court rules on your claim.
To determine the status of the bankruptcy case, follow this link: http://www.uscourts.gov/services-forms/bankruptcy
