Please note the interpolations:

On Monday, May 14, 2018 at 1:23:32 PM UTC-4, Jean-Pierre Coulon wrote:
Thanks for the manual, but I am not learning much.

This sythetizer had spent a few years on a shelf. After a few days with
the 220 V it restarted.

I am unclear whether it started (properly) after a few days, or it remains on standby mode?

I believe some accumulator was empty and it is
unable to boot in this case.

Present tense?

Hope it may help someone in the future :-)

Yeah. Actually reading a manual is typically my last resort.

Jean-Pierre Coulon