The IRS must incorrectly have you on file as having marketplace health insurance. A 1095-B does count for coverage but you are not required to enter the details, as the IRS does require with a 1095-A.
If you only received a Form 1095-B and it has "all year" or all 12 months checked, then submit a copy of that form to the number (fax is quickest) on the IRS notice.
You don't need Form 1095-b to file your tax return, It is for your information only. Just keep the form in your files.
