You need to RELEASE this button again to be able to validate and continue. This is mostly important when assigning controls to switches like on the Warthog Hotas or Honeycomb devices. Anything that continues to send the signal to the UI will freeze it.
For example: You assigned the red switch “down” on the Honeycomb Alpha to “Battery off”. To validate it you need to set the switch to “up” after it has been recognized.