Current conditions have created a significant challenge in keeping touch screens clean.
Firstly I suggest that you shutting down and unplugging the screen before cleaning but due to the urgency and frequency few do this now.
Check with your screen supplier, but I suggest that soap and a little water should be okay, although better still would be a suitable glass cleaner liquid. Do not use kitchen cleaners, bleach, ammonia solutions and vinegar as these can damage the sensitive coating on touchscreens. Alcohol is a maybe some screen manufacturers are saying that it is okay and say are saying this is a no-way.
One point I have noticed is that supermarkets do not care in the long-term, but most of us want our screens to last as long as possible so do not assume that because a supermarket uses it that it is okay.
Now disinfect by spraying the screen with a fine but thorough cleaner mist. Do not soak the screen or allow moisture to get into any of the openings on the table. Leave the cleaner mist on the surface for one minute.
Now wipe it off with a microfiber cloth or soft rag. Do not use abrasive cloths or paper towels as these can scratch the glass.
If required to remove dust and smudges from your screens, use water for the heavy lifting.
Now allow it to dry.
Now if your screen does not work, I am not trying to tell anyone how to suck eggs, but please check your power lead as it may be slightly out of its socket either at the back of the monitor or the PowerPoint. Also, check that the monitor cable is secure and in correct. We get all very annoyed now when our support line is flat out, and a person calls and the problem was that the power cable came out of the plug.