Outside of open enrollment, you can only enroll in or change Marketplace plans if you qualify for a Special Enrollment Period based on certain life changes or your estimated household income.
Loss of health coverage
You may qualify for a Special Enrollment Period if you or anyone in your household lost qualifying health coverage in the past 60 days OR expects to lose coverage in the next 60 days.
Job-based coverage: You may qualify for a Special Enrollment Period if you lose health coverage through your employer or the employer of a family member, including if you lose health coverage through a parent or guardian because you're no longer a dependent.
There are other qualifying life changes such as changes in household (getting married, having a baby, getting divorced or death) or changes in residence. Please see additional information on healthcare.gov