@Jenny we have seen that when you enable and disable features in the "Set up". The account will activate or inactivate with the enabling/disabling of the feature. The system notes on the account record will indicate the user that enabled/disabled the feature made the update to the account record. I would look through the features and see if any have been disabled/enabled features (corresponding to the system notes on the account). Here is a link to accounts which can be impacted this way.
https://netsuite.custhelp.com/app/answers/detail/a_id/64402/kw/accounts%20enabled%20feature