Thank you for reaching out to us. From the screenshot provided, clearly states guest users ( i see you have used gmail account to login ) don't have the privilege to enable sync.
Refer to this article https://learn.microsoft.com/en-us/azure/active-directory/enterprise-users/users-restrict-guest-permissions#:~:text=Restrict%20guest%20access%20permissions%20in%20Azure%20Active%20Directory - about different types of permissions can be defined for guest accounts in Azure AD
Request you to login with the account having Global Administration Privileges and try the same steps.
Let me know if you have any further questions.
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