navigating old ER bills with new insurance

Just received an ER bill from nearly a year ago, after switching insurance companies. Anyone else experienced this post-Change cyberattack delay? Looking for advice on handling old bills when you can't access previous insurance accounts. The statement shows an "uninsured discount" despite having coverage at the time. Any billing specialists who can shed light on next steps? #InsuranceHelp #ERBill #HealthcareQuestions