Self-Employed Health Insurance Deduction

Approaching retirement I am still  earning about 10K as a corporate trainer.  This income is reported as self employed business income from a 1099-NEC .   When I record approx. 5K  of business expenses against the income for Self-Employed Health Insurance Premiums it has zero effect on the net income.  If I test any other field on the business expenses (Legal fees, Business insurance, etc.), it works as expected decreasing the net income.  It feels like a bug since I have more than enough income to offset the expense.  Why does this field not work as expected?