While 1.5.7 may trigger a lot of warnings on PHP 8, it should still run.
You'll need to apply the fix that torvista eluded to: https://github.com/zencart/zencart/c...994aba823e09ea

When you get a blank page it means a fatal error has occurred. Usually that error is recorded in the /logs/ directory of the store's files. What's the error in your case?
https://docs.zen-cart.com/user/troub...ng/blank_page/