2004 Toyota Tundra - 4WD won’t engage

My 04’ Toyota Tundra won’t go into 4wd. Lights on dash flash from time to time and other times not , but still won’t go into 4H or 4L. Is there a service bulletin on this issue?

https://www.carcomplaints.com/Toyota/Tundra/2004/tsbs/

Nope, don’t see one.