Verdict
Structural — appeal rarely changes it
The denial reflects the plan's contract (an exclusion or an exhausted limit). Verify the payer applied the right facts, then move to the patient conversation rather than an appeal.
Unappealable when the accumulator is right — no letter restores an exhausted maximum. The only checks worth running: whether the payer's accumulator math is correct (prior claims processed to the right plan year) and whether any benefit rides outside the maximum under the plan's terms.