How do I get old apps like Photoshop CS5 to work on macOS Mojave
The first thing I would try is changing the security and privacy settings in System Preferences. You can do this as follows:


Go to Apple > System Preferences…
Click on Security &amp; Privacy
Select the Privacy tab at top right
In the lefthand pane select the Accessibility option
At bottom left of the window make sure the padlock is unlocked (if not, select it and enter your password)
In the list of apps on the right-hand side, make sure Photoshop and any of the other apps you’re having problems with are ticked
OPTIONAL: If any apps you’re having problems with are not listed, click on the + button under the list and navigate to the apps to select and add them to your list. Once done, then repeat Step 6
Make sure you lock the padlock again that you unlocked at Step 5
Quit and restart any apps you’ve just allowed to control your Mac (i.e. if they were already open)


Now try running Photoshop etc again to see if they work.