If your users are experiencing login issues via SSO, please check that the configuration quidelines have been followed. 

How to guide: https://support.zoom.us/hc/en-us/articles/201363003-Getting-Started-with-SSO 

Please also check that the SSO certificate has not expired. If the SSO certificate has recently renewed, it will need to be updated in the SSO SAML section of the Zoom portal. 

If you are still experiencing issues for logging in via SSO please open a ticket with AARNet support via support@aarnet.edu.au