Hey lithose,
Welcome to Apple Support Communities. To confirm, you've follow the steps below to set up/use AssistiveTouch, correct? The steps are also available here: Use AssistiveTouch on iPad.
Siri: Say something like: “Turn on AssistiveTouch” or “Turn off AssistiveTouch.” Learn how to use Siri.
Or do the following:
1. Go to Settings
> Accessibility > Touch > AssistiveTouch.
2. Turn on AssistiveTouch.
3. To customize AssistiveTouch, tap any of the following:
* Customize Top Level Menu: Tap an icon to change its action. Tap
or
to change the number of icons in the menu. The menu can have up to eight icons.
* Single-Tap, Double-Tap, or Long Press: Assign custom actions that run when you interact with the menu button.
* Create New Gesture: Add your favorite gestures.
* Idle Opacity: Adjust the visibility of the menu button when not in use.
* Confirm with AssistiveTouch: On an iPad with Face ID, use AssistiveTouch to confirm payments with Face ID instead of double-clicking the top button. Or on iPad (10th generation), iPad mini (6th generation), and iPad Air (4th generation and later), use AssistiveTouch to confirm payments with your passcode instead of double-clicking the top button.
If you set up an Accessibility Shortcut, triple-click the Home button or top button depending on which iPad you have. This step allows you to turn AssistiveTouch on or off without having to go to Settings: Use accessibility shortcuts on iPad.
If AssistiveTouch doesn't appear in Settings > Accessibility > Touch, we recommend contacting Apple Support for additional assistance. They can be reached here: Get Support
Best wishes.