Intertherm 56000 Btu Gas Furnace "keeping fan time" Questions

...fan on, glow plug on, gas valve open and fire to all 3 (or is it 4) flame tube... but the flame goes on for about 3 seconds and flame out... the process restart automatically 4 times and every time ...

...fan to run until the heat exchanger cools to @ set temp) has out lived its lifetime and needs to be replaced.the button is a manual reset that once reset would allow the unit to continue to run flame ...

...time in 3 weeks, the first two times we called someone out to fix it, but the guy our landlord calls takes like 5 days to come out here everyday he claims he will be out that day and I just want to ...