We have an employee that recently changed their name. Why would the following script produce an error if their email was correct at the time the script ran?

if (parentData && parentData.salesRep) {
                salesRep = parentData.salesRep;
            // Check to see if salesRep exists and was found in dataCache.employees object
            } else if (repEmail && dataCache.employees[repEmail]) {
                salesRep = dataCache.employees[repEmail];
            } else {
                validationFailed = true;
                errorArr.push('Sales Rep Email is missing or is invalid, cannot proceed');

The code alone doesn't tell me much. Step through this in the debugger and look at the variable values (or use print statements).