010 Cadillac SRX - Rear axle issue

the service rare axle sign keep appearing ,though I changed the oil twice, no one can pin the problem.
do you have answer olease

So the “service rear axle” sign keeps coming on?

You changed the oil and that didn’t fix it? No surprise there. Was the fluid level low? Was the differential leaking?

This tells you the service procedure for the problem. I’d add maybe the level sensor has failed but seems a rather daunting set of procedures, maybe a trip to the dealer is in order?