The password of the user that is used to monitor an Office 365 environment recently changed/expired. After this was changed, and the credentials were updated within Foglight, data collection resumed as normal. However, there was no indication within Foglight that this agent stopped collecting. The agent appears to be green/active, and there was only one alarm relating to "Management and Provisiong".
The only indication that this might have been a password issue is the following message from the agent logs:
YYYY-MM-DD HH:MM:SS INFO [Quartz[0]-38305] com.dell.agent.office365.collector.ExchangeOnlineCollector - RestUrl: https://address.office365.com/url eq 'TopMailSender' and StartDate eq datetime'2019-01-01T00:00:00Z' and EndDate eq datetime'2019-01-02T00:00:00Z'&$top=10&$format=Json, Response Code: 401, Message: Unauthorized