If you filed joint returns during the marriage, both spouses are jointly and severally liable for any shortfall, error or fraud. That means the IRS can come after both spouses for the shortfall, or only the spouse with more money, or however they want to.
You can file to request "innocent spouse" relief. This would include an argument that you didn't know about the error or fraud because it was hidden from you, or an argument that you should be partially responsible but not wholly responsible ("equitable relief"). The IRS is not bound by or required to follow the divorce order but they can include it as a factor in their evaluation.
(Don't get innocent spouse and injured spouse confused. Innocent spouse relief is when you are being held responsible for taxes due on joint returns from during the marriage, and you must be divorced at least 6 months before you can request innocent spouse relief. Injured spouse is for when a spouse wants to be protected from tax debts owed by the other spouse from before the marriage.)
The innocent spouse relief form can be filed as part of your tax return (if you expect an offset will happen) or it can be filed as a separate claim after you discover that your refund was offset or when you receive an assessment.
See here for more.
https://www.irs.gov/individuals/innocent-spouse-relief
