iMessage not activated
This morning I woke up to my iMessages not working. When I check the message section to make sure "iMessage" toggle is on, it says waiting for activation when the toggle is green.
It will send regular sms text however to recipients, for those who are non iPhone users or have the sms setting text on their iPhones enabled.
My phone has never done this before. I did no change to my phone last night or messed with any settings. I don't know how to fix this. I've reset/turned off my phone several times. I have an old iphone 6 plus. Despite being an older version its still okay to use. I do notice I'm still on iOS 12.5.5 and it hasn't sent me the next update for a while now. It's been on the same one for 6 months.
How do fix my iMessage situation. Help?
iPhone 6 Plus