If you are a Solibri perpetual license user, you use the same credentials for signing into both Solibri and Solibri Solution Center.
If you have forgotten your Solution Center password or wish to reset it:
Go to https://solution.solibri.com.
Click the Forgot password? link:
Enter your email and the new password (twice for confirmation) to the dialog that opens.
You should receive an email with further instructions on how to confirm the change. Please also check you junk email folder.