I'm trying to Upload the trigger below into our production environment and receiving the errors below. Test Coverage for the trigger is 85%. Not sure why I would get the errors below:

trigger ExpenseReportUpdate on Expense__c (before insert) {

Expense__c exp = Trigger.new[0];

date trx_d = exp.date__c;
Integer trx_m = trx_d.month();
Integer trx_y = trx_d.year();
String exname = exp.Employee_First_Name__c + ' ' + exp.Employee_Last_Name__c;
String exname_id;
String expR_id;
date trx_st = trx_d.toStartOfMonth();
date stdate = trx_st.addmonths(1);

    try {
        exname_id = [SELECT id
                    FROM User
                    WHERE name = :exname].id;
        }
        
    catch (QueryException e) {
        exname_id = [SELECT id
                    FROM User
                    WHERE name = 'Force Admin'].id;
        }
          
    try { 
    
        expR_id = [SELECT id
            FROM Expense_Report__c
            WHERE CALENDAR_MONTH(Statement_Date__c) = :trx_m
            AND CALENDAR_YEAR(Statement_Date__c)= :trx_y
            AND Employee__c = :exname_id].id; 
            
        exp.Expense_Report__c = expR_id;
       
        }
                    
    catch (QueryException e) {
            Expense_Report__c newER = new Expense_Report__c(Employee__c = exname_id, Statement_Date__c = stdate);
            insert newER;
            
            exp.Expense_Report__c = newER.id;       
    }
    
}

ERRORS I GET:

MyProfilePageController.testSave()            Failure Message: "System.QueryException: List has no rows for assignment to SObject", Failure Stack Trace: "Class.MyProfilePageController.testSave: line 78, column 35 External entry point"

"not even referencing this?"

ExpenseReportUpdateTest  Coverage of selected Apex Trigger is 0%, at least 1% test coverage is required

"coverage is 89%?"

Deploy Error Average test coverage across all Apex Classes and Triggers is 66%, at least 75% test coverage is required

"not sure why this is happening"