For people receiving advanced premium tax credits, if a payment due date is missed, insurers must provide a 90-day grace period during which consumers can bring their premium payments up-to-date and avoid having their coverage terminated, and the insurer is required to pay your claims during the first 30 days of the grace period. After that, during the second and third month of the grace period, the insurer is allowed to hold your claims and only pay them if and when you get caught up in your premium payments before the end of your 90-day grace period. (45 C.F.R. § 156.270(d).)
Note, however, that under certain circumstances, your state may require insurers to extend grace periods to policyholders who temporarily cannot afford to pay their premium. This may apply during public emergencies or following natural disasters. Check with your state department of insurance to see if your state requires grace periods in certain circumstances.