We've tried this before
There are many logical outcomes when ideas are generated, but two that are very common are that ideas are generated and they fail to achieve a viable outcome, so they are quickly discarded, or ideas are generated and no further action takes place, so idea generation is no leading to further action.
In the first case, the failure of an idea ("We tried this once and it didn't work") is really not a viable argument. We call this the Edison condition. Can you imagine what could have happened if Edison had decided after the first twenty or thirty attempts at creating an incandescent filament failed to quit trying? Clearly, the ideas that Edison and his team were generating weren't working. Edison is famous for finding 1800 ways not to create a lightbulb. Yet, he refused to give in to an idea that failed. Instead he continued to generate ideas. When an idea fails, all that the failure means is that the idea was "wrong" for the time, or opportunity, or conditions, or channel. It is possible the same idea can be applied successfully somewhere else. If your team adopts and accepts the thinking that failure indicates a dead end for ideas, then you'll create a culture that seeks reasons to shoot down an idea rather than one that looks for possibilities.
In the second case, ideas that are generated but never have any followup actions, this is a signal of process failure. If your team is generating ideas but there's no defined "next action", then you'll encounter a lot of frustration. Ideas that are generated but not followed up are quickly lost, and the teams that participated in the generation come to believe that idea generation is a waste of time, or a farce. This problem can be addressed by defining and creating an innovation process that defines how ideas should be acted on and how they should be evaluated.
If your team is generating ideas and it seems nothing is happening to them, diagnose the problem a little more deeply. Is the failure of an idea too easily accepted, or is there a lack of process to move an idea along on its path to becoming a new product or service?