If you’re a free member of Soltara, you would already have an account on Circle and it is likely that you haven't gained access to the spaces yet. If you have a membership link, click on it and sign in.
Do not create a new account.
The sign in link is located at the bottom of the form under "Already have an account? Sign in"
Once you sign in through this invitation link, the spaces will be unlocked.
If you don’t have an account, use the link to create one and follow the instructions.