Technical Punto Grande 1.9 Mjet wont turn/start?

[capsa43]

was sat for few weeks now wont turn over at all, turn the key get the lights but nothing, changed the fusebox as it has corrosion changed battery still the same, someone said earth starp but used jump leads to bypass and same, am lost anyone please help,

 

[Avocet]

Did you put a jump lead from the battery negative to the engine block? If so, leave that connected and take a SECOND jump lead from the battery negative to a good earthing point on the BODYSHELL (as well as the one to the engine).