You have to downgrade the core to 1.8.9.
In the IDE --> Tools --> Boards --> Board Manager --> SAMD21 Arduino, choose version 1.8.9. Takes a while, don't interupt. Then try again.
You have to downgrade the core to 1.8.9.
In the IDE --> Tools --> Boards --> Board Manager --> SAMD21 Arduino, choose version 1.8.9. Takes a while, don't interupt. Then try again.