I'm working with an Axxess system. It has a 9 amp power supply, cpu64(ver.5.2), 3 DKSC64+, 1 LSC w/ daughter card, and EVMC card. The phone system lost power to all of the phones while the system was in use. The power supply was reading the correct voltages and all lights were on all cards. Power cycling the system had no effect. Removing the power cord for 10 seconds allowed the system and phones to work again. However, if you power cycle the system the phones will not power up. You have pull the power cord for 10 seconds again, then it will power the phones. I'm trying to find out what the cause might be for this issue.

Several possibilities come to mind, but before going further I'd suggest that you perform a Major Reset from the software and then see what if any symptoms still exist.

I am having a simular issue but cannot get my phones to power at all. Were you able to resolve this?

I have seen on an Axxess system where if there is a modem plugged into one of the serial ports, it will stop the system from booting up. Once the modem is unplugged and the system is power cycled it will come right up. This is rare but I've seen it on multiple occasions.

Another test would be to pull all the cards except CPU and Power Supply. ***Caution: the EVMC is not hot swap!*** Push in one station card at a time and see if the phones on that card come online. I have seen a DKSC16+ take down an entire system.
The other is to watch "Message Print" to see if there is something else going on. A corrupt DB purhaps???
Also if something is causing enough errors that are writeing to the log file it will cause an insanity issue and drop the system to stop the errors.