Why can't I reset service 4wd I have a 05 Chevy Silrado with 63000 my service 4 wd indicator came on at 50000I reset it now at 63000 it's on again and won't let me reset. shift indicator lights inop?

My 2005 Chevy 4wd, ext. cab,shrt bed, has push buttons to go from(from top to bottom) Auto 4wheel drive, to 2 High , then to N(neutral), and then to 4 high, then to 4 low. At approx. 50,000 mi. the service indicator light came on and indicated "Service 4wd." I re-set the indicator, and forgot about it. Now, at 63,000 mi. it's telling me to service the 4wd, only this time the reset works until I turn the ignition off. when I restart, the service light comes on. However, the indicator lights that show which gear the transfer case is in, does not light up, and there is no automatic shifting of the transfer case. Is there a simple solution to this problem? Recommendations...Please! popo63