Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B410F1024GQ64/MSC/MASSLOCK#0x0
LOCKKEY=UNLOCKED
Mass Erase Lock Register
Mass Erase Lock
0 (UNLOCKED): undefined
1 (LOCKED): undefined
https://github.com/cmsis-svd/cmsis-svd-data