Have a look at the parts manual MM which contains wiring schematics. You want the chassis loom for models on and after 2014. You will see after the main 50 amp fuse (check seating of this) there is a splice (bombtail) of eleven red cables to share battery feed. One of these, R29, feeds the ignition switch. Others supply the first four fuses (1 - 4) with keep alive feeds. These in turn supply side lights, horn, hazards and a feed to instruments.
As a start check main battery cables including chassis connection. Then bombtail for presence of +12 volts and again before and after each of the first four fuses, comparing with voltage directly at battery as they should get very similar. Unlikely to be a load issue but if for example you find output of fuse 2 is at expected 12 volts then operate horn (same circuit as hazards) to see if it works or if voltage at fuse collapses. The bombtail is located on the main loom 50mm after the split to TSM/headlamp unit and fuse cluster.
The feed out from ignition switch is a green/yellow cable to another bombtail feeding six similar colour cables, one of which feeds fuse 20 exclusively powering heated seats. Again you could check for presence of +12 volts (with ignition on) before and after fuse although it appears to be a separate stand alone issue.
Given this info you should be able to trace battery power all the way to failed circuits to find culprit(s).
