STM32L476RGTx Nucleo Blink Code in Assembly[Newbie Ques]
I think you got the RCC_AHB2ENR register address wrong.

The base address is given as 0x40021000, the offset is 0x4C. So the address of the register is 0x4002104C and not 0x4002144C.

So in effect you do not enable the clock to the GPIOA, hence nothing will happen (I have not checked those addresses).

Another remark: your loop has no delay, the LED will not blink visibly for humans as it will be switched on and off in the MHz range. It'll look like half on.

Lesson: pay extra attention to magic numbers (always), try to use predefined symbols - then you have to pay extra attention only once.



Next error:

The GPIO Mode register of port A has a reset value of 0xABFFFFFF. ORing another 1 into that will not change anything.

You have to reset the setting bits for the pin you want to change first.