I have this problem. Only one PC but a new hard drive. I called customer support and spent almost an hour without success. They cannot disclose account information or change any information they have. All they could do was suggest that maybe in the past I had opened another account and maybe I could remember what the username might be. I then proceeded to Account Recovery and provided the requested information and pictures of my driver's license. I got an almost immediate reply and after providing more information I was presented with two accounts. One was long ago forgotten (I have been using TurboTax for almost 20 years). I was able to change the password, email and phone in this forgotten account and was able to successfully log in. I went back to reinstall TurboTax under the second username but when I provided the 16 digit license I got the same message - "license already linked to another account". And yes, the license number is correct.
Any suggestions??