It looks like there is some confusion over the wiring colours there. The red wire on your battery should be earth, this is easy to confirm, trace the red wire from the battery, I believe you will find it goes to earth, now remove it from the battery and run a OHM meter between the terminal and the engine block, any resistance? Thought not, thats the earth lead. The Battery is in the wrong way around +earth. Again, double check (measure twice, cut once), reconnect the battery the other way around, black wire to +, red to earth, that sounds so wrong! Now use your meter to check you have 12v + at the starter, you should have.
Daily drive is a Giulia 2.0 MA, wife drives a 939 Spider in the summer and a Abarth 595 in the winter. For special sunny days we have a S2 Spider Junior in the garage.