Hey! I was just having this issue as well. It suggested buying it through the web portal but when I tried to purchase the eSim, the payment button was greyed out.
I tried 1) uninstalling the app then reinstalling 2) toggling between airplane mode and 3) rebooting my phone, none of these worked. What finally worked for me - I logged into the Member portal and went to the "Purchase eSim" page. From there, I scanned the QR code to download the app, which took me to the app store. For whatever reason, this finally let me open the app without it showing the "Maintenance Mode". I hope that helps!
