All of my third party apps crash in iOS 26.6 on an SE 3rd generation iPhone

If there re any add-on VPN apps or add-on security apps, remove all, restart, and test again.

Specifically remove the apps too, as disabling some of these isn’t always reliable.

Any remote hosted-storage apps, or any add-on security apps?

Has the internal storage ever been completely filled up? No free space?

Next steps; Back up, factory reset, restore, test.

Failing that, you’re headed for a discussion with Apple Support.

I quickly push the volume up then volume down buttons and then hold in the side button, the phone just goes to the slide to shut down screen like if I only just pressed the side button. Any suggestions?

You are not following the instructions correctly for a Forced Restart. After you quickly press the Up and Down buttons, you have to hold the Side button until the Apple logo appears in the center of the screen. That means that you have to ignore the "slider" and keep holding the Side button until the Apple log appears.

Release the Side button when the Apple logo appears and the iPhone will restart.

"All of my third party apps crash in iOS 26.6 on an SE 3rd generation iPhone I just updated to iOS 26.6 and all my downloaded apps crash when I attempt to open them. I just get the splash screen for a second and it reverts to the home screen. The built-in apps work fine. I tried to do a forced reset several times, but even though I quickly push the volume up then volume down buttons and then hold in the side button, the phone just goes to the slide to shut down screen like if I only just pressed the side button. Any suggestions?"

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App Issues After an Updates:

Clear the System Data:

Sometimes, after an update, caches get cluttered. By removing System Data, caches would be rid of --all of which can lead to misconfigurations. Caches are created so that apps open quicker, or operate more effectively. Use my User Tip: How to Clear "System Data" in your iPhone's Storage: - User Tip

If the problem persists next time just offload any 3rd party app and then redownload it from your home page, this fixed the problem for me