It's a sad day for my mechanical skills

I've tried that and everything else in the book that I can work on . I think it has to be electrical . The obd readers suggest so also . .I just have no electrical diagnostic skills at all . This electric stuff is a very dark art to me.
I cringe when I read the solar power threads knowing full well that the words I read are just made up jibberish to make the author sound good and make me feel thick , and it works . NO ONE UNDERSTANDS ELECTRICKERY , AND DONT BELIEVE THOSE THAT SAY THEY DO .

 

Aliens. Aliens understand it

 

I am no expert on French cars, however being a Mercedes Diag tech i face similar issues on a daily basis. Code readers have their limitations as some faults may be stored ones from a while ago which didn’t stop the engine starting at the time but maybe a bit of uneven running.
As mentioned the immobiliser circuit could be causing an issue or even the ecu itself.
If the mobile tech has got a decent diag computer he should be able to get a bit further in tracing the issue. However experience of the product is key.

 

I had a Apple Mac 'repaired' as it was not firing up, by dropping the computer 6inches onto the desk as it was a common fault with the mother board loose! and charged £80 for that. I now switch off and on many electrical items with a problem and sometimes it works by clearing confusion and back to factory setting! Have a old MG and I mostly use a 1/2 inch A/F spanner, spade screwdriver and a hammer, such joy!

 

Solar cells and lead acid batteries are simplicity compared with the works of the Devil masquerading as cars made since the late 1990s.
Crush them all, once the three year lease is up, they are BER Junk.