Fluid currently will not allow you to login with user accounts that don't have a password set - this is a security measure. We're not going to change that, though we will add device-specific logins in the near future (i..e you'll be able to log in without a password once you pair a device with Fluid).
In the meantime, here are a couple of options to try out:
- Add a password to your existing user account. If you don't want Windows to prompt you for a password after startup, you can always turn on automatic logons in Windows 10.
- Alternatively, you can also create a new Windows user with a password and use that to log into Fluid.