My furnace "fails to start" 3 times, then it flashes 7 beeps and quits trying. I can hear it start then the flame "just stops" 3x in a row. What gives?
7 quick red flashes sequence means "lock out" in this case which is a generic for "it's not going to try to start again for an hour".
"Something else" is initially preventing it from starting, could be the flame isn't igniting (you can tell by watching it, does it ignite to blue flame?) or the flame sensor isn't working, etc.
What you need to do is carefully watch the beeps between starts when it first tries to kick on, it'll give you another code with the "real problem reason" instead of the more generic "3 attempts failed" which 7 beeps mean, which occurs after the 3 attempts.