2012 RT SE5 with repeat Start issues and Brake Failure light showing - any ideas?

1 - It looks like you need a new battery, or at least, get in there and check that the terminal connections are clean and tight.

2 - The brake failure message doesn’t just come on due to low pressure. It is also caused by low level in the reservoir under your seat. You have to have each chamber full. Very full. Check the white floats inside the sensor to make sure they are floating and not stuck. Fill until they are floating slightly above the outer ring of the sensor. Check the rubber diaphragm under the cap to see if it became extended. Just push it back into place. When you replace the caps, point the little vent bump to the rear.

3 - It's hard to know if the hard click had anything to do with anything. But ultimately, the only cure for a brake low pressure switch fault message is to do a brake fluid flush and/or pad replace as necessary. Could be time for a whole brake job. It’s a 2012 after all. And the only cure for an old, weak battery, is a new battery.

4 - The next time you have it running and the fault is active, call up the codes. Push the Mode, Set, Turn Signal Cancel all at the same time WHILE THE BIKE IS RUNNING AND THE CODE IS ACTIVE. Once you know the fault code, then you’ll know how to fix it. It's 13 years old. You'll be doing all your own maintenance.