Why does Messages on my Imac send and receive from some people and not from others?

Hi tynbai,

Welcome to the Apple Community.

tynbai wrote:

Why do Messages on my iMac and Ipad send and receive from some people and not from others? It works fine on my Iphone

Seems iPhone may have cellular data turned on for sending to Android phones.

Apple Support have an article online with more info. on the green and blue messages:

What is the difference between iMessage and SMS/MMS? – Apple Support 

Seems if wi-fi (blue wi-fi messages) is not available for any reason,

messages are sent over cellular (green text messages).

Cellular is necessary for sending messages to Android phones.

Seems your iPad and Mac are set-up to send iMessages over wi-fi,

yet not set-up for sending texts using a cellular data plan.

You may (or may not) want to:

Set up iCloud for Messages on all your devices - Apple Support

All the best :-)

You are most welcome, tynbai,

Thank you for replying, and for letting us know what worked for you!

Cheers :-)