Free busy from Exchange to Domino stopped working suddenly.
This was caused by permissions for the log directory of F/B being modified and accidentally remove exiting user permissions on those folders.
As a result Autodiscover and EWS web services become inaccessible.
This issue was resolved by restoring previous permissions and adding Authenticated users read permissions on the following folder.
...\WebServices\Autodiscover
...\WebServices\EWS
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