I'm receiving the following error for one of our custom objects. I don't understand what the error is and therefore can't implement the necessary fix(es). Can someone explain what this means?

EMAIL ALERT ABOUT TRIGGER
Apex script unhandled trigger exception by user/organization: 00560000006hY5t/00D60000000IoEk
ServiceDetailStageUpdate: execution of BeforeInsert
caused by: System.QueryException: List has no rows for assignment to SObject
Trigger.ServiceDetailStageUpdate: line 2, column 1

ERROR MESSAGE SHOWN IN SALESFORCE WHEN TRYING TO UPDATE RECORD
Error: Invalid Data. 
Review all error messages below to correct your data.
Apex trigger ServiceDetailStageUpdate caused an unexpected exception, contact your administrator: ServiceDetailStageUpdate: execution of BeforeInsert caused by: System.QueryException: List has no rows for assignment to SObject: Trigger.ServiceDetailStageUpdate: line 2, column 1

I can provide more details about the code if necessary.

Thanks in advance!

I'm receiving the following error for one of our custom objects. I don't understand what the error is and therefore can't implement the necessary fix(es). Can someone explain what this means?

EMAIL ALERT ABOUT TRIGGER
Apex script unhandled trigger exception by user/organization: 00560000006hY5t/00D60000000IoEk
ServiceDetailStageUpdate: execution of BeforeInsert
caused by: System.QueryException: List has no rows for assignment to SObject
Trigger.ServiceDetailStageUpdate: line 2, column 1

ERROR MESSAGE SHOWN IN SALESFORCE WHEN TRYING TO UPDATE RECORD
Error: Invalid Data. 
Review all error messages below to correct your data.
Apex trigger ServiceDetailStageUpdate caused an unexpected exception, contact your administrator: ServiceDetailStageUpdate: execution of BeforeInsert caused by: System.QueryException: List has no rows for assignment to SObject: Trigger.ServiceDetailStageUpdate: line 2, column 1

I can provide more details about the code if necessary.

Thanks in advance!