100% chance of failing a rush?

RNG hates you.

It's not that there's 100% chance of failing (unless it's bugged), you're just really unlucky.

Just keep trying you'll eventually complete them. You can try putting more skilled dwellers, such as more S in power rooms, as well as luckier dwellers. Both reduce the chance of failing a rush.

Note that the rush chance of success decreases quite dramatically after a rush (succeed or fail) so doing it many times in a row will make it harder to do a successful rush.

See this answer for more factors influencing rush failure rates: https://gaming.stackexchange.com/a/224005/106901

Luck is the biggest factor in success of rushing a room aside from the initial percentage (which is based on both luck and the time since a previous rush.) The primary ability doesn't appear to effect the rush rate, but instead the actual room output. I've had 10-S dwellers with low luck rush, and had just as many failures as low-S dwellers with low luck.

I did some experimenting and found that if you put a room full of dwellers with max luck, the initial percentage of failure is much lower than a room with non-maxxed/low luck dwellers. That being said, the more times you rush in a given time, of course the failure rate climbs. The only thing that will decrease that is time.

tl;dr: Try putting high-luck people in the room and see if your success rate increases.