Have you even checked your socket.io is installed or not / nodejs installed/running?
You need to check both node-socketio.error.log and node-socketio.log
As well as You need to check both redis-socketio.error.log & redis-socketio.log under /home/frappe/frappe-bench/logs
$ bench doctor
$ bench update --requirements
$ bench setup socketio
$ bench setup redis
$ bench retry-upgrade
$ sudo supervisorctl restart
$ sudo service nginx restart
You need minimum 1GB RAM, Check If your system is low on memory, because we seriously can’t help anything about it.