I was having the same frustrating problem, but my carrier is Verizon so I’m not sure if this will help you.
Here's what I found by googling the problem. Talk about convoluted and obscure! Good Luck!
"https://discussions.apple.com/thread/254533009
Group Text IPhone 14 Pro to Android Users
I have a new 14 pro and am no longer able to send photos via text or group text to a mixed use group of Android and IPhone users. HELP?
Posted on Jan 6, 2023 12:57 PM
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User profile for user: Lawrence Finch
Lawrence Finch
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Level 10
When you activate an iPhone 14 on Verizon their automated system does not set up MMS correctly. To fix it you need to call Verizon tech support (611 on your phone), tell the nice representative who answers that you need to speak to a senior tech to fix a problem with the provisioning of MMS on your account. This is a universal problem with the iPhone 14 provisioning by Verizon, so the tech should know how to fix it. And hopefully the 1st tier reps will eventually learn also.
Alternative Solution:
Laner84 has posted a do-it-yourself solution that works for most people →Just got iPhone 14 — can’t text android phones in group texts
https://discussions.apple.com/thread/254473731?answerId=258423448022#258423448022
Log in to your Verizon account. Select "Account" at the top of the screen-"My Plan"-"Blocks." After selecting the appropriate line, select "block services"- then toggle on "block picture and video messaging." After saving, wait a minute or two then toggle it back to off. After everything saves, a phone restart may or may not be necessary.
This is after you verify that MMS Messaging and Group Messaging are toggled on in your iphone Messages settings.
This seems to reprovision sms/mms without having to call in"