Images not being sent via text message

I have recently switched from Verizon to Xfinity.  Since then, there are certain numbers I cannot send images to in messages.  I get a Not Delivered returned to me.  But there are others I can send to with no issues.  This was not a problem before.

It happens on both Android and iPhone and they are specific not random.

I have researched the problem and have tried them all include Network Reset, making sure items were turned on, and I even did a Factory Reset on my iPhone so we were starting from scratch.

None of these worked.  I spent most of the day with Comcast support and their suggestions was everything I tried so they said to go to Apple.  I did that first and they told me to contact Comcast.

Anyone else experiencing this issue and resolved it?

PS: and it is not just me, my son has the same issue, but my wife and daughter do not.  We've check the IOS version and they are either up to date or a version back.