Welcome to Spyder World. Brake fluid level is something that is deceiving. You've noticed that the reservoir slopes downwards towards the front. The level sensors are those white plastic things in the rear of each chamber. So, even though the fluid level looks good, it can still trip the sensor, especially when stopping or going downhill, because the fluid sloshes towards the front. So, add just a little fluid in order to raise the float in the sensor to at least equal or just above the outer ring of the sensor. See pic.
Also, inspect the gasket in the cap. They expand out sometimes, and when they do, they interfere with the sensor. Just push the rubber back up into the cap. It will pop back into place.
Codes - When you have the brake failure code ACTIVE, or when any other problem is ACTIVE, you can call up the code by simultaneously depressing the MODE - SET - TURN SIGNAL CANCEL pushbuttons. The code will be displayed on the LCD display. You can do a forum search then and get information, or ask. BTW, the code for low brake fluid level is C0049
It is helpful to purchase a downloadable service manual for these things. For yours, it's only around 20 bucks. Google search. There are a couple of vendors for that. Green Manuals is one.
Because you are new to the Spyder, it will be helpful to read through this thread as it applies to the 998.
https://www.spyderlovers.com/forums...t-Do-s-and-Do-Nots-quot-for-new-Spyder-owners
If you need an owners manual, that is missing a lot of times with pre-owned machines, you can download one here. Just use the drop down menu in the upper left to navigate to 2012 RT.
https://www.operatorsguides.brp.com/Index.aspx?lang=E&s1=792d64bc-9944-4f44-9b19-822acd37f62b
And depending on the maintenance history of that machine, it will be helpful to you to search the forum and read up on replacing vacuum lines, spark plug wires, and doing a canisterectomy. All things that will keep you riding and not working on it. Be safe out there. Watch out for deer.