Hello,
I am not sure if this bug is caused by Harvest Festival itself, but it seems like Yulif is not actually building anything when he should. I discovered that bug while testing "Renaissance" on a server hosted by someone else, so I can not provide logs as of right now, and probably no accurate ones when I am able to.
I assume that this bug may be related to Sponge as the Server Owner insists on using Plugins and Sponge in general, I have not experienced this bug in singleplayer or multiplayer without Sponge/Plugins either. Basically this was the result:

If inaccurate logs are still alright I will ask the owner for them later.

Thanks for your report!
Unfortunately Harvest Festival does not support Sponge. If you can reproduce this with just Harvest Festival and Forge, please open a new issue.

Apparently the bug is not caused by Sponge directly, but by a plugin that restricts block placement (some "claim land" plugin). I will try reproducing it with a forge mod if that will make it a valid issue.