Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32l4/STM32L412/USB/FNR#0x0
frame number register
Frame number
Lost SOF
Locked
Receive data - line status
Receive data + line status
https://github.com/modm-io/cmsis-svd-stm32