The Top Down template TopDownController has Block Input enabled by default. This is potentially confusing for new users not aware of this difference.
Note that due to [Link Removed], testing this requires adding a key input to something below the Controller in the stack, such as the Character or Level Blueprint. Block Input being enabled will block the input from firing.
Reproduced in 4.7.6, 4.8 Preview 3, and Main (//depot/UE4/Promotable-CL-2554325)
1. Create a new Top Down template project
2. Open the TopDownController Blueprint
3. Open the Class Defaults
4. Find the Block Input setting
Block Input is enabled. Note that due to [Link Removed], you can't test it this way in 4.8 or 4.9. Instead, add a key input in the Level Blueprint or TopDownCharacter Blueprint and set it to Print String: it will not run during PIE.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-15849 in the post.