From our investigations it appears that you renamed an AI Classic project from .zip to .aia. This allowed you to load the project into AI2, but because the file structure and content is different, no blocks were shown.
@SteveJG was able to cleverly interpret the instructions to replace the blocks.
In essence, for future reference, you cannot load AI classic projects into AI2.
I renamed your (AI1) aia to .zip, opened the .zip file and removed Screen1.bky. Then I converted the .zip file to an (AI2) aia file (using the AI1 to AI2 Converter).