To join Signite you must first have a working Google Workspace account, and login to Signite using a Super Admin user.
Failing that, you may receive a Please contact your Google Workspace administrator message.
To make sure you have the permissions necessary to create a Signite account, go to your Google Workspace account, and make sure that your user has the Super Admin role assigned to it.
If login issues persist, you can try to first install the Signite app from the Google Workspace Marketplace, and give it the necessary permissions.
Follow this guide for the installation process:
Following the app installation, login to Signite and verify your account from the Permissions screen.
If you need further help, please contact us at firstname.lastname@example.org