I created my own SID, as it were, using the FMC in order to abbreviate what otherwise would be longer flights. I started from KVCV near my home, and then followed the ZIGGY3 STAR to KONT. Above 400 ft LNAV engages but not VNAV. No problem. I figure it has something to do with the abridged route I programmed into the FMC. However, when switching from FMC to MCP to get set up for Final HDG SEL illumines but does not turn the A/C. Firmo indicated a similar problem in another post. I also have to change MCP Alt up or down slightly to get V/S to respond to acquire pre-selected MCP altitude.
I have a hunch that departing an airport for which there is no SID and following a STAR to final without a transition point, fouls things up.