Thanks for the investigation! I have checked all devices we have and confirmed the problematic ones are all with Trues Asset Version 1007, while the working ones are with version 1009.

We had some other findings. So we had 3 testing phones upgraded to iOS 26 public beta previously, and encountered this issue. Then we tried to upgrade to iOS 26 official and this issue persist. Yesterday we tried to reboot these phones above, 2 of them are working while the other one still does not. We also upgraded 2 more iPhones directly from iOS 18 to iOS 26 OFFICIAL, and everything works fine. So I'm suspecting this might be something related to iOS 26 beta. Any input would be appreciated. Thanks!

Sorry I'm not a network expert, but ChatGPT helped analysed the certificate and reported it's "missing full chain" - The chain is "leaf + intermediate only", while it's supposed to be "leaf + intermediate + root". While I have forward to our network team, is there any way to bypass from app as a temp fix? Thanks!