How to fix push not sended
If you sometimes didn't get the notifications or notifications are delayed, that's probably because your cron job system is not triggered.
Use cron-job.org
A solution to fix this is to use https://cron-job.org/ to force the execution of the push cron job every 5 minutes.
Just create a new task to ping the url https://www.YOURWEBSITE.com/?pagename=wpappninja&type=cronjob