What IRS says about that letter is not what you say it says:

What you need to do if you received Letter 6217C

• If we confirmed we received your response to Letter 5263C or Letter 6042C, you do not need to take any action. We’ll contact you within 180 days if we have questions.
• If we requested more information about your business, estate, or trust, provide the information requested in the timeframe provided on the letter.
• If we notified you that the employer identification number (EIN) information on file is not correct, submit Form 8822-B, Change of Address or Responsible Party-Business.

https://www.irs.gov/individuals/understanding-your-letter-5263c-6042c-or-6217c