Yamaha XV 1100 No ignition, no start

Tomorrow, year 95 My neighbour has made me, battery is charged 12Volt but should be replaced. Seat removed when I turn on the ignition lights up nothing with the instruments but it clicks on the Big Black box under the seat, it does not start either, so does not react to the push of a button and starter does not receive a signal. Do I turn off the ignition briefly the Green Idle indicator. is there still a fuse? Is idle in and stand is e s also not, or yet the battery too weak? or a relay broke over winter? Machine still ran last year. Edit: what noticed, is that the gas grip is fixed, I could not look yet, has the possibly a TPS sensor on it so that it does not switch through because that is something from the resting state? mfg. Peter