Not sure if you are using a laptop or not. But if you are, check Settings>Power that blank screen is not set 15min (as mine is).
I’m not a user of Caffeine on my Linux rig, but have used it successfully on a work PC under Windows, to keep display alive during presentations etc. Long story, but corporate IT Admin installed Caffeine rather than change power settings for one staff member. I assume this Caffeine app is the same thing for Linux, which simulates small mouse movement to fool screensaver there is activity. You can find it by searching Software on Zorin.
(edit) I am not sure which of these is most appropriate, but see you are running Lite, so the gnome shell extension is probably no use.
