Notifications from Teachme Biz usually arrive within a few seconds to a few minutes.
However, delays of up to several tens of minutes may occur under the following circumstances.
- Congestion due to concentrated processing on our servers, notification services, or Apple's notification servers
Additionally, notifications may be stopped under the following circumstances.
- The device receiving notifications is set to Do Not Disturb mode, airplane mode, or other settings that stop notifications
- There are issues with the communication or startup status of the device receiving notifications
Related: What are the means of receiving notifications?
https://help.teachme.jp/hc/en-us/articles/11000688986137