First of all you can't efile an Amended return except for NY. Amended returns have to be printed and mailed.
Then the amended return replaces the original return. Online only saves the last one. You need to save your original return as a pdf to your computer before amending.
I have a similar situation. I cannot locate my amended return (1040) on my computer. After I printed it to mail it in, I can not retrieve it and I get an error 190 code.
For Error 190 you need to download the state program
After you get the program reinstalled the first thing to do before you open your tax return is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).