Hi! I understand you're encountering a "something went wrong" message when trying to log in to the Tandem app on your iPhone with iOS 18.5. Let me help you get this sorted out.

First, may I ask a couple of quick questions to understand better?
- Are you able to open the app and reach the login screen, or does the error appear immediately after entering your login details?
- Have you recently changed your password or any account details?
- Have you tried logging in with the same credentials on another device or on the Tandem website, if available?

Meanwhile, here are some common steps we can try that often fix these types of login issues:

1. Check your Internet Connection
Make sure your iPhone is connected to a stable Wi-Fi or cellular network. Sometimes, poor connectivity triggers “something went wrong” errors.

2. Restart the App
Close the Tandem app completely by swiping it away from the app switcher, then reopen it.

3. Restart your iPhone
A quick reboot can clear temporary glitches.

4. Update the Tandem App
Ensure you are running the latest version of the app. Open App Store > tap your profile icon > scroll to check if updates are available for Tandem and install if yes.

5. Clear App Cache or Reinstall
On iPhone, you can delete the Tandem app and reinstall it. This often clears corrupted data causing login problems.
- Press and hold the app icon > Remove App > Delete App.
- Then reinstall from the App Store.

6. Check Tandem Server Status
Occasionally, Tandem's servers experience outages or updates causing login errors for all users. While I don't see any official outage notices right now, some user reports on forums show similar errors sometimes1 .

Try these steps, and let me know at which point you see any change or if the same message persists. That way, I can guide you further with advanced options or escalate if needed.

Are you comfortable starting with these?