-sweat drop- System File Shield

When ever i click for Avast to be turned on it says that the system file shield is missing. I’ve tried re-downloading it but it didn’t help. When I try to turn it on from the Avast program it’s self it looks like it’s loading but then there’s nothing. Can anyone help me?

Do you have any other AV installed on this PC?

No I don’t. (Sorry for taking so long to reply)