Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Microchip Technology/ATSAML11E14A/SERCOM0/SPI/CTRLB#0x0
SPI Control B
Character Size
Data Preload Enable
Slave Select Low Detect Enable
Master Slave Select Enable
Address Mode
Receiver Enable
https://github.com/cmsis-svd/cmsis-svd-data