First, ensure your iOS is up to date by going to Settings > General > Software Update, as updates often fix bugs that affect accessibility features.
Then try enabling AssistiveTouch through Settings > Accessibility > Touch > AssistiveTouch, and toggle it on. If the toggle is grayed out or unresponsive, try restarting your device and attempting again.
If it still doesn't turn on, go to Settings > Accessibility > Accessibility Shortcut and ensure AssistiveTouch isn’t selected as part of a conflicting shortcut.
You can also try enabling it via Siri by saying, “Turn on AssistiveTouch.” If none of these methods work, perform a Reset All Settings via Settings > General > Transfer or Reset iPhone > Reset > Reset All Settings.
This won’t erase your data but will reset system settings that may be interfering. If the problem persists after all these steps, it could indicate a deeper software issue, and reaching out to Apple Support would be the best next step.