Thank you @sjrcpa, I was being hopeful the 1040x started a new clock, but thank you for confirming it does not.  Can I file 1040-X all the way back to 2015?  I thought you had to file an amended return within 3 years (including extensions) after the date you filed your original return or within 2 years after the date you paid the tax, whichever is later.

Thank for your help!