TurboTax never knows about back taxes you owe, so no one at TT can tell you why a collector is contacting you. Who is the "collector?" It might be a scam or it might be legit----we have no way to know. Are they saying you owe the IRS? The state? A local or city tax?
Generally, if you owe money to the state or the IRS, they will send several letters before sending to collections. Is there any reason you might not be getting official mail from the IRS or your state?
You can get your IRS records here.
https://www.irs.gov/individuals/get-transcript
Start by looking at your account records and tax transcripts from 2020 to verify the debt is real (not a scam) and see if you can figure out why there is an assessment. It might be that you forgot to add some income, or the IRS believe you had income you didn't report due to an error or identity theft, or some other issue. You may need to ask a local tax professional help you decipher the IRS records to figure out what when wrong, and whether the IRS is correct in their assessment. Then finally, you may be able to negotiate a reduced settlement with the IRS if you are able to pay it in full.