Which SSO package/version are you using?
Please provide specific error message that you see:
Are all users affected? If not, please provide sample email addresses of affected users:
Is this affecting only the primary domain or secondary domain?
Is the issue reproducible on other browsers,computers, networks?
Do you experience redirects, or does authentication fail outright?
Does the issue only affect particular G Suite? If so, which?
Please provide step by step screenshot/screen cast leading up to the error / issue page.