Error Handling/No results from SQL Query

[buran]

obviously your SELECT statement does not return anything. And thus cursor.fetchone() returns None. As a result your previous code was raising an exception. Now it just continue.
try

def checktable():
        problemid = PROBIDENTRY.get()
        connstring = 'DRIVER={SQL Server};SERVER=OBDEVSQLAGL05;DATABASE=DCollection;UID=xxxx;PWD=yyyy'
        SQLstr="select OWNER from GD_SERV_ADMIN where PROBLEMID=?"
        conn=pyodbc.connect(connstring)
        cursor=conn.cursor()
        cursor.execute(SQLstr, problemid )
        row = cursor.fetchone()
        if row:
            messagebox.showinfo("Owner found", "The ADMIN for this problem ID is:  " + row[0])
        cursor.close()
        PROBIDENTRY.delete(0,END)