I've had and continue to have many issues with MIL/CEL, blind spot monitors and this illumination unavailable message. Yesterday I received a call from two Stellantis techs, not the dealer service techs. They told me the warning light for the illumination unavailable was due to my on-going blind spot monitor issue and appeared to be something triggered every 300 miles. I just got a call from the dealer stating that the "clearance on my instrument cluster pins was too loose" and they have now ordered a new instrument cluster. He could not elaborate if it was also related to the blind spot monitor so I'm going to have to wait until someone can talk to the Stellantis techs.
Honestly, I've been told so many different things and I'm still not fixed that I don't have much confidence this is going to fix it either, but fingers crossed!