Do you have an owner’s manual? See what that says.

Don’t know what it specifically means on your car but I would start by checking the brake fluid level in the reservoir. If it is very low or there is none there is your answer. That would certainly trigger the warning. If you don’t see fluid I wouldn’t drive it anywhere except to a local service station that can check for leaks in the hydraulic system.

There is a chance it is just an electrical glitz. Once on my 2002 VW Passat the red engine warning ⛔️ light came on while highway driving. I pulled over, let the engine cool and checked the oil level. It was fine…:) So I fired it up, drove off and never saw the warning light again!

Good luck!
J
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Will I buy another Volvo??? We'll see....