This is something that we usually have the students do at school. We have found that this fixes 80% of all possible chromebook issues.
If possible, please have your child do at least steps 1-2-3 (update OS) at your earliest convenience. Steps 4-5 are optional, but help too. We posted this in Google Classroom for the students as well. Thanks for everything that you are doing at home with your children. We know that it's not easy and we appreciate your efforts.