Adobe Photoshop CS5 extended installation error

[ABRUNI]

 I had to reset my older imac and uninstall all my apps. My operating system is el Capitan 10.11.6 (15G22010). CS5 Extended was working fine on this opertating system. Now I'm trying to reinstall the same apps I had before again. 

I did a search and found my product CS5 extended on my account, and followed the download instructions but keep getting this message when i hit the install icon:

"Install" is damaged and cant be opened. You should eject the disk image

Tried doing this several times unsucessfully.  Any advice! Cant upgrade operating systems on this mac or buy a new one yet.  Aby tips or advice are welcome!

I'm assuming im going to face the same problem with lightroom....

[thatsmauri]

The error might be related to macOS's Gatekeeper security feature.

Try the following:

1. Go to your Mac's System Preferences > Security & Privacy.
2. Click on the padlock icon in the bottom-left and enter your admin password if you're prompted to do so.
3. Select Anywhere under Allow apps downloaded from:.
4. Close the System Preferences window and run the Installer again. You may get additional prompts shown, but the installation should work now.

Be sure to revert your security settings back after the installation is complete.