Hi there! I see that you’re encountering the 'Oops invalid message' error on your Pioneer Press e-Edition app on your iPhone running iOS 18.6. I want to help you get this sorted out.

To begin, could you let me know when exactly this error appears? For example, does it show up when you open the app, try to log in, or while reading an article? Also, have you already tried any fixes like restarting the app or your phone?

Once I have a bit more detail, I can guide you through some clear steps. In the meantime, here are some general things to try:

1. Force Quit and Reopen the App: Swipe up from the bottom of your screen and pause in the middle to bring up the app switcher. Find the Pioneer Press e-Edition app and swipe it off the screen to close it. Then reopen it.
2. Check for App Updates: Open the App Store, tap your profile icon at the top right, and scroll down to see if there is an update available for the Pioneer Press e-Edition app. Updates can fix bugs causing errors.
3. Restart Your iPhone: Sometimes a simple reboot clears temporary glitches. Hold the side button and volume up button until you see the slide power off, then turn your phone back on.
4. Check Your Internet Connection: Make sure you have a stable Wi-Fi or cellular connection. Sometimes network issues can lead to messaging errors.
5. Log Out and Log Back In: If you can access your account, log out, then log back in to refresh your session.

If those don’t fix it, the issue might be with the app’s cache or your account permissions. Let me know what you’ve tried and what happens at each step, and we can dive deeper or I can guide you on contacting support if needed.

Are you able to try these steps now?