use this thread below in helping you to determine whether your entitled to take your loss. it's limited to your 1) original investment plus 2) any income included in your tax returns over the years plus 3) any tax-exempt income over the years less 3) any losses deductible on your tax returns (does not included suspended passive losses) over the years less 4) any distributions received over the years less 5) any expenses under the tax laws that would not be deductible such as travel and entertainment (this does not include suspended passive losses). the result is your "basis".
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if you conclude that a writeoff is proper then you indicate in Turbotax that the current year is a final year and you've disposed of your entire interest. this will allow the suspended passive losses to pass through. if the losses exceed your "basis" you'll have to use the at-risk form 6198 to limit the deduction to your "basis"
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https://www.thetaxadviser.com/issues/2020/may/deduction-worthless-partnership-interest.html
while this refers to a partnership it would also be applicable to an investment in an S-Corp
