SMS group chat not working with iOS 18

I have a preexisting group chat with two non-iPhone users that has never not worked before. I also use a VPN that has not given me any issues with the message app. After updating to iOS 18, I could not receive messages in this group chat if my VPN was on. I’ve tried turning it off, and that worked once with the new RCS messages, but I do not want to leave my VPN off. Now I cannot receive any messages in the group chat, whether the VPN is on or off, whether the RCS messaging is on or off. Single SMS messaging works fine. I’ve restarted my phone, I’ve restarted my network settings, I’ve deleted and readded the VPN configurations

I don’t care about using RCS, so if part of the solution is to keep it off, that is fine by me. I just want to keep my VPN on and to be able to receive texts in my group chat. If anyone has any suggestions, please let me know!