TurboTax Online apparently made an error

My 1040 line 15 had a positive amount between $10,000 and $20,000, yet line 16 was filled in with zero.  I filed married filing joint return.  Everything I looked at tells me that the tax should be 10% of line 15.  Seems like a basic mistake and probably a programming (??) error.  Can't find any way other than this forum to report this or ask about it.