How do I chain vert and street tricks in Tony Hawk's Pro Skater 1/2/HD?
Solution 1:
Back in Tony Hawk Proskater 1(original game, not hd), you were unable to perform a manual. In the second game, they added the manual, but you are still unable to manual after performing a tick from a pipe. Even if you pressed down/up, up/down before landing off a pipe, you cannot combo that trick. Street tricks/rails can be chained with manuals by pressing up/down, down/up as mentioned in the other answer.
I have played all three games mentioned and I am also finding inconsistencies with chaining using manuals in the updated HD game. It seems as though the HD re-make is not polished enough to consistently record a manual after performing excessive grinds/street tricks. Also, it is impossible to chain a manual to a vert trick in THPS HD, unless you buy the Revert DLC Pack, and then it is possible to chain the tricks using a revert move.
Solution 2:
Revert was given free in a patch before the DLC was released. You do not need to buy the DLC revert pack in order to receive the code adding revert to the game.