It can be taken at any time, but now would require forfeiture of the shares. For tax year 2019, the loss could have been taken without forfeiture.
Remember, though, it is only good to offset gains on other investments. It is unlikely that anyone who’d invest in a company that was liquidated and shut down will ever have gains to offset.
I swear I’ll never use the phrase “you can’t make this stuff up” ever again after being on the OTC. Apparently you can.