Fixed. Using the information here: https://github.com/OpenSC/OpenSC/wiki/SmartCardHSM#initialize-the-device
$ pkcs11-tool --login --login-type so --init-pin
Using slot 0 with a present token (0x0)
Logging in to "SmartCard-HSM (UserPIN)".
Please enter SO PIN:
Please enter the new PIN:
Please enter the new PIN again:
User PIN successfully initialized
Login now seems to work!
$ pkcs11-tool -O --login
Using slot 0 with a present token (0x0)
Logging in to "SmartCard-HSM (UserPIN)".
Please enter User PIN: