Just noticed that cookies are no longer effecting spotlights in the latest version?
Can recreate by creating spotlight in a new scene and adding a cookie image, no longer effects the light.
Example project with just a spotlight, cookie image and plane
The engine has been switched to clustered lighting … and that has cookies disabled by default. Go to the Settings->Rendering and enable them there.
See more here: Clustered Lighting | Learn PlayCanvas
Ah ha! Thanks! faith in humanity restored