Fix push notification issue in PHP for a swift project

I have a iOS project where we are sending push notifications to the users with FCM. The database contains around 28000 tokens where the php file send push notifications. But from past few days the devices are not getting push notifications. When I tested the app by sending push notification to my single device UDID, it worked. But it is not working for all the devices in the database. When I checked in postman, I got "405 Not Allowed" error. since you need to fix only this issue, my budget is Rs. 1000. You need to fix the issue by screensharing on teamviewer.