Following up on Carl's suggestion to start at the battery;
Go both ways- unscrew and check both battery cables.
With cables off you, can use your voltmeter to see where you have complete circuits.
I think it is good practice to clean both ends of the negative cable. The same for the positive cable.
There is at least one big fuse in the electrical box. Sometimes the big fuses can look intact, but be open. If the large fuse is blown, I would try to find why it blew before replacing.
I would also check both the start key switch, and the contacts, and make sure that the wires are all well attached in the interconnect under the dashboard.
All the best,
Peter