Perform diagnostic on Lennox package system. Upon arrival homeowner stated that a error message would pop up on thermostat periodically not allowing any heating or cooling in the process. Found system tripping main limit switch causing the system to shut off on high limit code.Found gas pressure at 3.69, adjusted gas pressure to 3.45, And ran system for 15 minutes. System ran with no issues and no error message popped up on thermostat after. Informed homeowner that if errors still occur, we may replace thermostat as thermostat may be having a software issue. System is operational at this time.