IMessage / texts not working after 16.4 IOS update

To activate iMessage and FaceTime using your Phone number

First, check to know whether you have an SMS plan enabled at least for One SMS*** with your carrier. Contact your Carrier (Cellular Service Provider) the agency that issued the SIM to you

If your iPhone is used with a carrier not found in the wireless carrier articles, make sure you can send and receive international SMS. (One SMS*** Only)

If you can't turn on or sign in to iMessage or FaceTime - Apple ...

*** You may not have an SMS plan enabled by your carrier for the SIM/eSIM that you use on your device. Apple Inc does not provide SMS services.

Please check if you have a stable internet for iMessages to work consistently.

Connecting to Wi-Fi is the initial step, followed by establishing an internet connection.

However, it's important to note that connecting to Wi-Fi does not automatically guarantee an internet connection. In the event that you are unable to connect to Wi-Fi, the issue may stem from settings on your iPhone or the router/modem.

On the other hand, if you are unable to establish an internet connection despite being connected to Wi-Fi, the problem is likely related to the settings on your router/modem. In such cases, it is advisable to promptly contact your Internet Service Provider (ISP) for assistance.

Check your WiFi Router / Modem for --> Recommended settings for Wi-Fi routers and access points ...

For your Internet connection.

• Over Cellular: contact your Carrier (Cellular Service Provider). The agency that issued the SIM to you
• Over WiFI: Contact your ISP (Internet Service Provider), the agency that provided the Internet Service on your Modem/Router to you

However --> Connect iPhone to the Internet - Apple Support

iMessage (Blue) -

• iPhone to iPhone: requires internet (Either over WiFi or Cellular Service) as it is sent over internet protocol. Needs Activation on your device.
• iPhone to Android: Not available

SMS/MMS (Green) -

• iPhone to Android: does not require any internet it is sent over cellular voice protocol. Needs to be enabled by your Carrier for the SIM used by you.
• iPhone to iPhone: When iMessage is not activated or the device is not connected to the internet either over cellular or WiFi
• You need to have an SMS/MMS plan enabled by your carrier for the SIM/eSIM that you use on your device. Apple Inc does not provide SMS/MMS services.

It will turn from Blue to Green if you have enabled "Send as SMS" and whenever your iPhone is not connected to the internet it is sent as SMS (green) to all iPhone users.

I had to work with Verizon on this for a couple of hours. The problem may be two-fold. One, for some reason after the 16.5.1 update my phone number was removed as a source for texting. My email addresses were still active. Go into Messages and make sure your phone number is checked on Send and Receive. Last, Apple appears to have automatically turned on the Focus feature. WTH - don't want it so don't do it. This can cause some apps to not work all of the time with users.

I have an iPhone 12 max. I hope this helps.