I've seen this once before where the system was activated by a different user, and that users account is no longer around/disabled.
To fix you would need to go to all of the system flows in Default Solution and turn them off and then on.
IOM Provider Transformer
IOMActionExecutionEventInsertHandler
IOMActionExecutionEventProgressTracker
IOMStepActionEventEvaluationProcessor
IOMStepActionEventInsertExpiredHandler
Create Fulfillment Orders
IOMRetryExpiredMessageRequests
Create Fulfillment Plans
IOMStepActionEventInsertHandler
Process Fulfillment Source Assigned Sales Order Line
Create Account Mapping
Create Contact Mapping
Thats a starting list, see if it gets you past this. If not reach out to me.
Thanks
