Please try to update `TR` configuration as specified below:
Update those at the **SAML2SSO** profile configuration.
From the available NameID formats add `transient` or `unspecified`.
At the attributes release:
choose ``TransientID, Email, username``, and others that you want to add.
update, and restart gluu server.
Follow this link: https://www.gluu.org/docs/gluu-server/4.1/integration/saas/onlyoffice/
Let me know the updated result.