thanks @AlidaOdendaal
thanks @saintaardvark
working now by tweaking allow an app through controler folder access
never had such a problem before with win10.
been using yumi, rufus and so many tools for many years.
just now, when i tried to use yumi, i got an error message, could not change boot record.
so that might be the exact issue, that windows now considers boot sectors are system protected.
i recently updated to win10.2004,
perhaps that update tightened the security, more than in the past
and i checked the list of protected folders and usb and sd cards drives are not listed.
but states that windows system folders are protected by default.
but i found this in the list of block history
