My 2003 XKR convertible with 80000 miles continues to message 'cruise not available.' I replaced the brake switch 2 weeks ago. I seldom had check rear lights messages. I always have No Cruise within 10 seconds of putting car in gear. There have been no further rear light messages.
There are no codes showing. Evap system test always fails.
The system is adaptive cruise control. Anyone able to point me towards the next steps I should take? Really need some help here. Thanks.

You mention a few problems. The best path forward at this point is to let the car tell you more, i.e. figure out a way to get the diagnostics codes. Unfortunately, you need a Jaguar/LR reader, or at least access to it.

One option is the dealer, as a one-time diagnostic visit.

There are hand-held options on eBay, etc. Folks have reported various level of success...

There is also the more comprehensive diagnostics software running on a laptop.

Best of luck, keep us posted.