iPhone 12 Pro won't connect via Bluetooth to 2009 Mazda 6

I just upgraded from iPhone XS to 12 Pro and can no longer connect to my 2009 Mazda 6.

iPhone will not recognise the Mazda and does not list it in available devices.

XS used the same version of iOS and Bluetooth as the 12 Pro, so I have no idea why this is suddenly a problem, and the Mazda has no problem connecting to my partner's iPhone XS.

What could possibly be so different about Bluetooth functionality on the iPhone 12?