How to fix 'iMessage Activation Failed' error on iPhone?

Contact Apple here:

Contact Apple Support - Apple Support

Too many of your messages have been reported as Spam by others, so you are blocked from using the service any longer. This may be a temporary ban or a permanent ban, but only Apple will be able to help you.

Messages is only intended for Personal use where your communications would not likely be repeatedly blocked by your friends/family members. Using it in a commercial setting where your communications may be unwanted is a violation of the terms of use for your Apple Account. For businesses, there are third party alternatives that use bulk SMS messaging services that do not use iMessage at all, and you will also want to check with your cellular provider as some have business accounts for that purpose.

Welcome and thank you for reaching out. 🤗

If Messages was deactivated due to spam reports, you need to contact Apple Support directly.

They can review your account and help reactivate Messages if it was mistakenly flagged.

In the meantime, avoid sending mass or unsolicited messages to prevent further flags.

Thanks again for reaching out. 👍🏼

Good Luck! 👋🏼😉

Smiliñ 😎 Brian | Community Volunteer