Signals Notebook: Sign button in experiment review process disabled until comment is added

Description

A user was unable to sign or invite a reviewer in an experiment because the Sign button appeared grayed out. 

Solution

The issue was resolved by entering a comment in the provided text field, which enabled the Sign action. This behavior is consistent with an administrator setting that requires a comment before signing.

Step to solve:

- Verify whether the experiment requires a comment before signing (this may be enforced by admin configuration).
- In the sign dialog, enter a brief comment in the comment field.
- Confirm identity if prompted (e.g., enter credentials or follow SSO prompt).
- Click the Sign button; it should now be enabled.
- If the button remains disabled, refresh the page and try again, ensuring the comment field is not empty.
- If requirement is unexpected, contact an administrator to review signature/comment policy settings.