Purchase Stocks under SEC Regulation CF How do I deduce the loss of that investment?

5 years ago, I purchased stocks under the SEC Regulation CF (Crowd Funding) via the website StartEngine.  Those stocks have failed and so I am trying to work out how do I deduct the loss of my investment.  I never received any documentation from these failed investments other than a Certificate confirming my investment.

 

If someone could direct me to where I need to go please.

 

Thank you

 

David