For security reasons, Parse Server is only supporting push notifications using master key and therefore push notifications can’t be sent directly from client anymore. You can see more details here:
The best practice now is to create a cloud function to send the push notifications. So your cliente will call the cloud function that then will send the push notifications.
In order to help our customers, we developed a code example of how you can create a cloud function to send the push notifications:
To call cloud functions from client, you can use the reference below: