I ran into some issues around step 113 when I tried to copy and paste my own HTTP-based API request straight to SF. I followed the steps and it looked like it went through correctly, then it glitched and a white screen showed up. I tried to refresh and do the steps over again but I got the same results. And nothing my name doesn't show up when I look under Today's leads.

It will always leave a blank screen in your browser, whether it works and adds the lead successfully or not. But if the lead isn't showing up under Today's Leads then it could be you have something wrong in that long string - even one character out of place will make it fail and there is no error message. Or your Flow is messed up and prevents any lead from being added.
See the Help FAQ for solutions. Always check the Help FAQ first for instant solutions.