Many ISPs disable this button. If grayed out, updates are fully automatic only.
Manual flashing voids your ISP warranty if you brick the device. Only attempt if you have a JTAG recovery setup. nokia fastmile 5g firmware
1.2000.00.00.157 (notorious for AX driver crash). Fix: Downgrade to 1.1910.04.00.022 or upgrade to 1.2101.xx . Many ISPs disable this button