I have an MFJ taxpayer with 1 qualifying child and 1 other dependent (ODC).  Write offs have reduced the tax liability to zero and the refundable portion of the Additional Child Tax Credit isn't generating.  Currently, the taxpayer is getting a credit of $493 for the qualifying child, and I believe the $1,500 refundable portion of the ACTC should be further offsetting the SE tax owed (currently over $6,000).

Is this a known software glitch?