Anyone who currently wants to use iMessage will find that sending messages is not possible in many cases.
The Apple system status page is currently reporting an error with the iMessage service. info page According to the report, the messaging service is suffering from a disruption that was already identified by Apple at 4:10 p.m. It states:
Users may not be able to access this service.
Based on some reports on social media, some users are currently unable to send iMessages to their friends.

iMessage: The authentication server does not always respond
Additionally, customers may encounter an Apple ID login screen because the authentication server is temporarily unavailable. There's not much you can do as a user except try on a different device and/or wait for Apple to fix the backend issues. In the iMessage interface, blue bubble messages that fail to send will appear with a red "Undelivered" label in the conversation. Affected users can try to resend the message by tapping the bubble. (Photo by Denys Prykhodov / Bigstockphoto)