Got a excellent deal on a little used Nuova Simonelli Mac Digit single group that was only in service a little over a year, and has been properly stored for the last 20 years or so. Gave it a once over and everything looked good. I attached it to the water softener/plumbing line installed for a previous machine and went to fire it up.
First issue was the pump wasn't turning, though the motor was trying since you could hear the hum. Disconnecting it from the pump showed that the motor was running fine, but the pump hadn't been run in so long that it was hung up. Turning it with some pliers fixed the problem, and once reconnected the pump quickly filled the boiler (confirmed via sight glass).
The problem is that the unit won't forge ahead with warming the water in the boiler and building up pressure. Press the power switch and the pump runs for about a minute (even though the boiler is full) and then shuts off, with the power switch light blinking at a faster rate than when the unit is shut off and waiting for powering up.
Waiting for 30 minutes or so to see if the pressure built up produced nothing - the bar needle on the manometer (upper needle) never moved. The lower needle went to the middle of its scale when the pump was running, but then bottomed out when it went off. The element works, since I could feel the boiler warm somewhat after trying this process a few times, but it seemed to only be warming when the pump was running, and shut off when the pump did.
So it seems like the unit wants to fire up, but something is prohibiting it from doing so, and the quickly blinking power light seems to be trying to warn of something. The NS manual from their website was unhelpful.
The dosing buttons can be activated during the minute or so when the pump is running, allowing water to exit out the grouphead. I used this capability to run a couple of quarts through the machine to help flush things out, and the water was running virtually clear when I finished.

I read somewhere in the forums that there is a secondary thermostat switch of some 'sort above the element, but I checked that and it did not seem to have been tripped. At any rate I couldn't move the (very) small red button I found there.

Any ideas will be very much appreciated.

Hi, the Mac cup single group controller will direct the pump run until the water level sensor is tripped (water at the right level in the boiler). There is a safety control check designed in the controller curcuit that will kill the power to entire unit after the pump runs for ~90 second at which time the power led will flash approx 2x per second. I think that you may need to investigate the water fill probe or the curcuit in the controller that deals with the water level sensor and how it controls the pump.

The gauge seems to be working properly since the upper gauge only moves if the boiler is heated and there is pressure in the system. If the power has been shut down to the machine as described above, the upper gauge will be reading zero. The bottom part of the gauge measures water supply line pressure and the immediate pressure when the pump is activated.

If the pump is running whenever you reset the power switch and then the led blicks quickly I think that it is the safety design that is causing that. Please post what you discover and the solution to fix the issue.