Whilst Gil is probably correct, and being one of the devs, very likely correct

that " The DMX Flood should work" why confuse things for a simple WS2811 flood. KISS principle

Just use a single line with
1 node per string (assuming the floods you are using are something like these
https://www.aliexpress.com/item/32912497979.html ) Not sure why the other person suggested 2 nodes?
Your example the effect is 2 minutes long, which does make the transition from colour to colour very slow. Suggest for testing purposes, to reduce that to say 10-20 seconds.
I noticed that your colour gradient the colours don't change, and box under the padlock icon was set to an up arrow. Try changing that thing (not sure what that box is called, see screenshot below) to the clock icon. Worked for me.