@jamescataxes
I also just thought of something that may explain your situation. You wrote:
"I'm filing as single with about $7000 of business income and about $15,000 of SSDI (though that is not counted as income but maybe it has an effect?). I have have a tax owed due to self employment tax so the credit would be useful."
You only mentioned self-employment tax. Do you have any income tax liability on your return? Or is your only tax liability from the self-employment tax? Self-employment taxes are considered "other taxes" and are not income taxes.
The Retirement Savers Contribution Credit is a non-refundable tax credit, which means it can reduce one's income tax liability down to $0, but not below. A non-refundable credit, such as the Retirement Savers Credit, cannot reduce self-employment tax.
So if your income tax is already at $0, that may explain all this, but I'm a fellow user and not a tax expert. Since I've already summoned @dmertz let's see if he confirms this during the day.
