opel vivaro not starting after reversed jumped cables attached

As the vans battery was still connected the damage is usually isolated to fuses.

Have you checked the fuses on top of the battery under the red cover? There's 6 fuses 3 large and 3 smaller. One or more of the 3 larger fuses are more than likely blown, most likely the 3rd one down fuse C which is a 500A fuses for the starter motor. But you should obviously check all 6.

The 3 large fuses can sometimes look ok when they are not so double check with a test light or multimeter.

According to the wiring diagram the starter solenoid connects directly to the ignition switch and not through a relay, so because everything else works the feed to the ignition switch should be there.

If all fuses are ok you should then check the main live directly the starter and then the signal wire that goes to the starter solenoid.

thanks terry i dont know whether you are in a different country and your vivaros are configured differently but my battery is under the floor pan on the drivers side, there are no fuses near it, only as i said on the side of the dashboard against where the door closes, these are more for ancilliary stuff, windows horn etc, and in the engine bay there is the one as you look at the van on the right hand side under the coolant expansion tank, here are the bigger fuses and relays, i did check them all and as you say there is a 500A one, they did all look ok, i will check them again tomorrow with a multimeter, is there a relay that could be to blame? do you think that even after maybe a second it could have burnt out the wire to the starter or solenoid ? thanks for your reply i appreciate all help

by the way i posted this as i didnt know how to ask you directly if its even possible