Hello and thank you for helping.
Unfortunately i can't enable UAC.I am quadriplegic , as a result i can't use mouse or keyboard.Instead i use a headtracking software called "smile mouse" (it turns head movements into mouse movements).Problem is that when UAC pop-ups appear , the software stops working and can't click anything so i have to keep it disabled.
I tried download from microsoft store at my other pc in same network and it totally works but on my laptop which i have the problem still doesn't.
I opened the Settings app, clicked on "Apps" but couldn't find microsoft store anywhere ,although i managed to reset microsoft store but problem not fixed.
I run the System File Checker (SFC) and Deployment Image Service and Management Tool (DISM) to check and repair system files.It seemed to find some corrupted files and fixed them but problem not fixed again.