The following screen shot explain the issue well, in which there is no key assigned for the right alt key or alt gr. This situation cause a problem with keyboard layout switching when the current active layout is set to Arabic I could not use right alt + shift in order to switch to English, but in English layout it works fine. I have tried all Arabic variants but without success, all of its previews missing the right alt.
3rd level is not set to right alt and the issue is still the same. There is no right alt key defined in the Arabic layout!