I used a 327 for about 12 years, up until last December. If you have a DOS control, hitting the"e" key will bring up a list of error codes. (From the automatic screen, I think, as well as the g-code editing screen). They can be kind of cryptic, due to bad Italian-English Translation.
The .090 code is not really an error. It's on when you start the machine, and any time the power is off, you'll see it. Does it power up when you push the white button? If not, the .090 code isn't going to point you in the right direction.
The most likely errors you'll see, are input timeouts (1532.00 or something like that, forget the format). That and g-code errors, which you should be able to figure out by the descriptions. If you get any PLC errors, try shutting off the main power for 15 seconds, and restarting.
If you have any questions, I'll help if I can.