Can you sue? Probably. Is it practical to sue? No.
Your claims for improper administration of your employee benefit plan is subject to the rules of ERISA. ERISA is a terrible statute that makes it impractical to litigate anything other than matters that have a very large amount of money in controversy.
There are certain administrative processes you are required to exhaust before you can sue. Read your plan documents and commence whatever procedures are set forth in those documents. Once you have exhausted those procedures, if you still are without coverage, you should find and consult with an ERISA attorney.
Good luck to you.
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