Re: Door not unlocked even though key collected

The Trial key will be useless until you unlock that big Padlocked Door down in the deep sewers.

To do that you'll need to go back into Town Hall while it's open and turn to the right as you walk in. On that side you'll see a Seagull and next to that Seagull on the crates you'll see a Key which you'll need to buy with regular Stars. That key will open the Padlocked door and reveal the portal to the Gnomiverse where the Doors to the Trials of Gnomus are located. Once you enter the Gnomiverse it's just a matter of exploring until you find the door with the matching color of your key- once you approach that door close enough the keyhole will glow if you have the right key and you'll then be able to use it to unlock the Trial.

Be aware that the Trials are just that- tests of your skill set as a player. Depending on your abilities you might be able to complete a Trial in one run through or you might be struck trying for hour and hour. Some of them could be extremely frustrating but you only have to finish each one once- and when you do be absolutely certain to save the code that you are given at the end and save that code until you've finished all four Trials because you'll need it.