macOS 12.4 & iOS 15.5 Message Synch Problem

JoanneL3,

On your iPhone, in Settings > Messages > Text Message Forwarding and turn off your iMac, then turn it back on. You should have to confirm with a verification code.

If the situation persists, on your iMac go to Messages > Preferences > iMessage and sign out of iMessage, restart your Mac and sign in again.

Keep us posted on any questions.

Hello JoanneL3,

Welcome to Apple Support Communities!

If you're having trouble sending and receiving messages from certain contacts, use the details here:

"Try these steps first

1. Restart your device:

• iPhone
• iPad
• iPod touch

1. Check your network connection. To send a message as iMessage or MMS, you need a cellular data or Wi-Fi connection. To send an SMS message, you need cellular network connection. If you turn on Wi-Fi Calling, you can send SMS messages over Wi-Fi.
2. Check with your carrier to see if the type of message you’re trying to send, like MMS or SMS, is supported.
3. If you’re trying to send group MMS messages on an iPhone, go to Settings > Messages and turn on MMS Messaging. If you don't see an option to turn on MMS Messaging or Group Messaging on your iPhone, then your carrier might not support this feature.
4. Make sure that your device has enough space to receive images and videos.
5. Make sure that you entered the correct phone number or email address for the contact."

This Apple Support page has the full details: If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

If the issue remains, is this happening on SMS, or iMessage, or both?

We hope this helps.

Cheers!