is it correct ?
but ball not moving
If you already create action for each direction string you can put the 8Direction pressing simulation there. Since you are using Gamma & Beta orientation make sure test the project using gadget that has accelerometer.
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You may need to request motion/orientation permission.
construct.net/en/make-games/manuals/construct-3/plugin-reference/touch
If this doesn't work, create a small test project with a text field and set it to Touch.Alpha on every tick, see if the value changes.