Yes it is related to group permission. To solve the problem create the missing directories
[/var/www/html/wp-snapshots] and [/var/www/html/wp-snapshots/tmp] and set permission to 755 to thoses directories
sudo chmod 755 /var/www/html/
sudo chmod -R 755 /var/www/html/wp-snapshots
If it doesn’t work with 755 try 777 but do not leave it that way on a production server
