New Windows 10 Insider Preview Fast and Skip Ahead Build 17661 - May 3 Insider

I went to restart Windows Update service, which I've seen sometimes help this kind of problem, but it took multiple minutes to restart (always a bad sign when restarting a service), and in the end it failed. Perhaps there's a WU issue with our current build. It's not like WU has been used for anything in 17655 (beyond Windows Defender updates, which barely count) for us to know.

Same here...tried a reboot it's trying again. However I see that it has not actually downloaded the update yet..doesn't it do the download before 'preparing to install' ?

My Fast Insider that was stuck at 80% is finally downloading.

Now downloading. Patience is indeed a virtue....