I am having the same issue.  2019 amended return will not electronically file.  When I try to convert/transmit, that line turns yellow in Homebase.  I don't even get an error message. 

Yes, all updates done.  I did find a solution to mine at least.  While the original filed return was open, I clicked on E-file to try transmitting yet again.  I noticed the 8th item down the list says "Amended Return Ready to EF".  It was NOT checked.  I don't know why but when I checked it and tried transmitting again, it went through.  Hope this might be helpful.  Thanks!

Unless something has recently changed, Intuit does not allow 2019 amended returns to be e-filed.  Only 2020 amended returns can be e-filed.

They opened Efiling of amended returns in the summer of 2020 for 2019.  

2020 is the first year that we can Efile amended return that we didnt prepare the original.

Thanks for the correction Lisa.   🙂

Thanks so much! It worked!

I updated and it helped! Thanks!

This helped me also. Thank you!