I followed the instructions at http://tropicraft.net/downloads/, but new items did not show up in Creative inventory. I have started the client with the default launcher. How could I solve the issue?

Hi,
Are you using a copy of minecraft with Forge installed? If so, would it be possible to provide any sort of console log?

Game output:

2015-02-14 18:08:25 [CLIENT] [INFO] Setting user: Mate0728
2015-02-14 18:08:25 [CLIENT] [INFO](Session ID is token:3521d4a86560479e8e5c5988d07fd886:7baff69a38724aa2a306a0124d06a60c)
2015-02-14 18:08:26 [CLIENT] [INFO] LWJGL Version: 2.9.0
2015-02-14 18:08:26 [CLIENT] [INFO] Reloading ResourceManager: Default

Starting up SoundSystem...
Initializing LWJGL OpenAL
(The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
OpenAL initialized.

2015-02-14 18:08:37 [SERVER] [INFO] Starting integrated minecraft server version 1.6.4
2015-02-14 18:08:37 [SERVER] [INFO] Generating keypair
2015-02-14 18:08:37 [SERVER] [INFO] Preparing start region for level 0
2015-02-14 18:08:38 [SERVER] [INFO] Preparing spawn area: 62%
loading single player
2015-02-14 18:08:39 [SERVER] [INFO] Mate0728[/127.0.0.1:0] logged in with entity id 407 at (183.89190030118127, 71.0, 246.7068001175465)
2015-02-14 18:08:39 [SERVER] [INFO] Mate0728 csatlakozott a játékhoz
Setting up custom skins
2015-02-14 18:08:42 [SERVER] [INFO] Saving and pausing game...
2015-02-14 18:08:42 [SERVER] [INFO] Saving chunks for level 'tropicraft'/Overworld
2015-02-14 18:08:43 [SERVER] [INFO] Saving chunks for level 'tropicraft'/Nether
2015-02-14 18:08:43 [SERVER] [INFO] Saving chunks for level 'tropicraft'/The End

I don't see any trace of Forge, although the installer run successfully

Perhaps try re-installing forge?