I can't log in to TD Ameritrade

You can try restarting your phone—>Restart your iPhone - Apple Support

Beyond that, you can try deleting the app, restarting the phone again, then adding it back.

If neither of these solve the problem it’s an issue with the app. Go to the App Store and see if perhaps it was just updated.

You should be able to log in to the site using a web browser. If that doesn’t work (and you’ve tried on multiple devices) it’s a problem on their server end.

What did TDAmeritrade say when you contacted their technical support?

No, it is not on Apple’s end.

It is on TDAmeritrade’s end—>https://downdetector.com/status/td-ameritrade/

Did you click the link I provided, where over 7,000 people reported that it was a problem with TD Ameritrade? Or don’t you believe in facts?