If your insurer is leaving the market altogether and won’t offer coverage on or off the marketplace, it must provide you with notice of its withdrawal and discontinuation of coverage at least 180 days before coverage is discontinued. Other state specific requirements may also apply. Since you are losing qualifying coverage, you should be eligible for a special enrollment period.
If there are no other insurers in your area offering marketplace coverage, you may want to see if there are any off-marketplace plans available to you, although you won’t be eligible for financial assistance with non-marketplace coverage. Additionally, your state’s Department of Insurance may have information on what to do in this is particular situation. (45 C.F.R. § 147.106).