You are not alone. Apple officially discontinued Lion (10.7) years ago, and the original download links from the Mac App Store are long dead. The remaining copies floating around the internet are often incomplete, improperly patched, or simply broken.
Then use the open-source tool dmg2img to convert the broken DMG to a raw ISO: mac os x lion 1072 dmg file fixed
e3ce4016da27b96e3bd5fb2d49366295d3ff4876 You are not alone