An error occurred during activation try again later keeps coming up when I try to use iMessage

Hello Lmr1365,

Welcome to Apple Support Communities. 

We understand that you’re getting an error when trying to activate iMessage. We are happy to help.

Please try the steps here as they may resolve this: If you can’t turn on or sign in to iMessage or FaceTime - Apple Support

"Check your device settings

1. Make sure that you’re connected to a cellular data or Wi-Fi network. 
2. If you're using an iPhone, you need SMS messaging to activate your phone number with iMessage and FaceTime. Depending on your carrier, you might be charged for this SMS.
3. Go to Settings > General > Date & Time and make sure that your time zone is set correctly.

Turn off and restart iMessage and FaceTime

1. Go to Settings > Messages and turn off iMessage.
2. Go to Settings > FaceTime and turn off FaceTime.
3. Restart your device:

• iPhone
• iPad
• iPod touch

4. Turn iMessage and FaceTime back on."

If there is no issue resolution, please contact Apple Support here: Contact - Official Apple Support

Let us know if you have further questions.

Take care.