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Do you know how many total circuits are affected? Where are you taking the readings?
Sorry for the delay. Had a phone call from another customer.
This sounds like a dead leg of power. The only reason you would get a good reading on each main is because it's reading through the double pole breakers. If you turn off all double pole breakers, you should be able to isolate one of the mains as being dead.
Or, it could be the main breaker that has the problem.
Is that when taking a reading from one main breaker lug to other main breaker lug?
When the meter probes are oriented that way, the reading should be around 240 volts, as you probably already know.
If that's the reading you are getting, then the main breaker itself is the problem. Are you able to post a photo of your panel, with all breakers shown?