Find missing photo not working

Where do you keep you photos? An internal hard drive, an external hard drive, a NAS , the Cloud???

I feel like Adobe is making changes to functions that worked in the past but don't work now.

No, there has been no change from Adobe. What happens when you click on the missing file indicator? Is there any message or warning or error on the screen? If so, what are the exact words?

In a first step try is to reset the preferences to the default settings.

Reset Procedure:

• Close Lightroom.
• Windows: Hold down [Alt]+[Shift] while restarting Lightroom.
  Mac: Hold down [Opt]+[Shift] while restarting Lightroom.
• Overwrite the Preferences when prompted by the dialog.
• Close Lightroom.
• Restart Lightroom.

It's recommended to backup your preferences before you reset the preferences to the default settings: 

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

If this doesn't help, please provide a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.