Generally, cancelled debt is considered taxable income. (You got money, you never had to pay it back, therefore it is taxable income.)
You can exclude part or all of the debt if you are insolvent. To claim an exclusion for insolvency, you need to fill out the insolvency worksheet in publication 4681 to determine the amount of the exclusion, and you need to file form 982 with your tax return.
https://www.irs.gov/publications/p4681
https://turbotax.intuit.com/tax-tips/debt/guide-to-debt-cancellation-and-your-taxes/L9YsOVhgB
Form 982 is included in Turbotax but I don't know how to access it. If you enter the canceled debt as a 1099-C form, you may be asked about insolvency, or you can try looking under "special circumstances" or search for "form 982" or "insolvency" in the search menu.