Having trouble with fast travel. While in White Orchard, clicked E on many signposts but they never turned green color on world map. Now am in the castle and am stuck as far as being able to travel to Velen. When I press E at the castle door, able to bring up world map, can see bullseye of present location in castle and the bullseye on the Velen map. Cannot figure out how to initiate travel between the two locations. Anybody know what I need to do?

Did you try space key after you use e key

Yes, doing so willl change the view from local to world.

Sounds like you didn't finish something that would have allowed your travel to velen/novigrad.

You press E & then space to bring up the world map & and then click on Velen & press E (or double click on Velen)
Then you should be able to double click on "The Hanged Man's Tree"

The current quest is to travel to Velen. I can see Velen on the map with a bullseye marker on it but nothing happens when I click on that bullseye marker.

Finally got it figured out. On the map there is row of symbols near the top of the page that tracks the type and number of places that have been visited. In my case, the signpost symbol was turned off so that none of the signposts showed up on the map. Turned it on and now I can see the signpost for hanged man's tree and all is good. Thank you everyone for your help.