96 Jimmy 4x4 issue

This summer I had to replace the radiator on my sons Jimmy. When doing so I started it forgetting to hook up the transmission cooler line. This caused quite a bit of fluid to be lost before I figured out my stupid mistake. I topped off the transmission fluid after cleaning up the mess and away he went. Today (winter) he informed me that it would not go into 4x4 high or low. The lights on the dash work but no activation of 4x4. Would this be related to the spill replacing the radiator? Is there a separate fill for the front differential? What sort of things should I look for?

No not related to trans and there are a bunch of posts on why the 4wd does not ativate most common are a rotted vac line under hood drivers side, then the 3 port vac switch on the transfer case, or a vac line up to the front axle vac actuator which pulls the cable to the pass side axle coupler. After that TCCM or encoder motor.