This is the fix!! So many things on this post didn’t work for me, but this is the solution!
This unfortunately did not work for me…
Changed the protocol. Reinstalled vpn config on phone. Restarted phone… group messages still failing to send. Hopefully a solution arises
Go to VPN app, settings, VPN Protocol, I changed to IKEv2, restart the VPN.
Express VPN chat person went through the whole thing with me, cleared up the issue.
It’s working fine now, all pics & texts go through to Android.
I’m using the original messenger app that comes with iPhone
“Text messages”.
Also off topic but don’t use messenger 
I have a vpn router and had this issue with ios update once tbh, took a few tries to get through. my guess would be a lot of traffic from expressvpn servers means apple sometimes filters it out. i would expect a privacy first company though to develop technologies to differentiate legitimate vpn usage from ddos
Just curious - is this still working? I’m having the same problem. Thanks!
Still early but this seems to work for me (haven’t yet txted Android group with pictures). Disabled the Block internet when unable to connect to VPN. However, not clear what privacy we are forfeiting when setting this. Not ideal.
I’ve noticed this recently as well, exact same circumstance. Incredibly annoying. hope they make an update to fix it soon.
This worked for me thanks so much!
As in Facebook messenger or just the default message/iMessage app on your iPhone? So maybe you’ll know this, maybe not, but I’ll ask anyway. I’m trying to figure out a good solution for maintaining my privacy and security while messaging non iPhone users, without making them download another app. I’ve tried getting people to use an encrypted messaging app but everyone says “I don’t want to download another app” lol like it takes 30 seconds… nobody cares about privacy in the US. Anyways, my best solution is to use an app called “text free” that allows you to create an alternate phone number to send/receive SMS texts from over data/WiFi. Is this a good solution or is there a vulnerability I am overlooking?
Go to VPN app, settings, VPN Protocol, I changed to IKEv2, restart the VPN.
It depends what you’re trying to achieve.
In a way you’re anonymizing who the other person is texting but obviously they have to know it’s you so if you’re looking for privacy from law enforcement that will do nothing for you.
SMS messages can still be intercepted in any scenario and if you ever use names in your conversation that’s your shroud of anonymity gone between the phone number not tying to you in any other scenario.
You’ll also want to check thoroughly the privacy policy of the app you’re using. I’m sorry I don’t have the effort to overlook it but you should look that messages are only processed during sending and there is no server backup but just on your device.
To stray a bit from your question; iMessage is the best option for encryption and you can have full privacy by disabling iCloud backup. Signal is my go to for android friends however you may struggle to get them on it — it’s a full fledged messaging app though that is ran by the organization that maintains the signal messaging protocol (used by WhatsApp). The protocol is the basis for encryption and privacy, Facebook obviously strips this for their app.
P.S. if anyone would like to argue WhatsApp is properly encrypted, restore your chat logs using only phone number and tell me how that works. No doubt Facebook stores them encrypted but definitely has the means for decryption themselves.