i'm trying to figure out what i have done wrong. i never had this problem before. i load up the fmc with my route and make sure my vpeeds are set. i set the mcp to v2 +10 on takeoff . once above 3,000 i engage vnav. it will connect up to the first altitude atc assigns once it's captured that altitude and i dial in the next it does not connect. Am I missing a step somewhere. should I leave the bottom altitude restriction blank on the vnav page. since i normally hand fly sometimes above 5,000 ft. i'm lost.....

You have to do something that's not quite obvious compared to the other aircraft. On the 737, there's a button called ALT INTV, but on the 744 this is not present. Press the center of the altitude wheel, instead.

 

...and while you're on your next cruise portion in the Queen, make sure to drop by PrecisionManuals.com, go to the Download page and find the Boeing 747-400 Type Rating Courses. They're similar to tutorials and a must read to get the fullest out of the plane.