Hi, thanks for submitting your question today. I will refer to the employer's disability policy as "DI" and Social Security Disability as "SSDI" for the remainder of this answer to avoid confusion.
You can go back and contest the denial of DI depending on the terms of the policy and how long you have to appeal an administrative denial. If you have surpassed the time to appeal, you may be precluded from appealing. Also, if you appeal and are denied again, then the only remedy is to file a lawsuit against the plan in federal court, for which I'd suggest you get an attorney. Be aware that you are precluded from offering evidence in federal court if you do not present it at the administrative appeal.
You should be aware also that most DI providers these days have a provision in their policy that requires that their disability payments coordinate with SSDI. What that means is that the amount that DI pays or owes you is reduced by the amount SSDI is found to owe you. Lastly, most DI policies these days have a claw-back provision that states whatever benefits DI paid out while awaiting for a SSDI decision or retroactive payment may be owed back to the DI insurer. I mention this just to inform you that, it may not even be worth it to pursue the DI past an administrative appeal because of this required coordination of benefits.
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