Unable to download clean Mojave installer - cannot make boot disk or upgrade

All three of my computers (two running HS, one brand new iMac running Mojave) cannot access an uncorrupted Mojave from the app store for boot disk or upgrade purposes. Can't delete the defective installers either. The older computers have outdated Mojave files that need to be DL again, but the app store sees that they are still in the the applications folder and only shows "open." After waiting hours for my new iMac to DL Mojave, not only did the DL not finalize (incomplete), but I was told that now it's damaged too and cannot be used. When i tried to re-DL a fresh copy from the app store, I got the same message. CATALINA is not an option!!! ~I need to remove the old programs and find a clean source.~