When I place a villager on the strange dead flowers, nothing happens. The blockage has been cleared for a few days now. Is a master builder required for this or is it a bug? Sometimes it will briefly say "watering field" but then quickly pops back to "nothing" under activity.

You don't have to have a master builder. You'll need to do some more research in a certain area.

For the spoiler page, click here!

I've read the link and still don't get it. All of my technologies are at 2 except farming which is at 3.

Ok, let me get this straight. You have level three harvesting, level two on all the others. The creek has been cleared so there is water in the lagoon, right? You drop a villager in the “dead flower patch” and they start to go but then stop? Try dropping another villager there and watch hem/her complete the cycle. If you close the program before he completes the cycle that will cause you a problem. Give that a try and let us know if it was successful or not

You are correct about my technologies completed. When I drop them in the patch (I've tried several villagers), it will say "sees strange dead flowers here" but then go directly to "nothing" almost everytime. In the event that it says "watering field," the villager will take one step and then action goes back to "nothing." Some of my villagers have been wandering over there at which time it will say "curious about field."

and yes, the creek has been cleared and the lagoon is full of water

LOL finally got one to do it. I think I was placing them too close to the edge instead of in the middle of the green patch.