This is a new install of PS. Testing it now, and I've found that signs are not working for plots within a city. I first tried putting a Buy sign up with this format:

[Buy]
50 Dollars

My understanding is that by using the text, it defaults to the economy system. The sign creates no problem, but [Buy] does not change colors, and other people right clicking on it does nothing.

Next I tried Rent:

[Rent]
20 (264)
6d

Tried this with both Dollars and items (Diamonds above). I get the following error in red text in game with this with Dollars:

Cannot make a field sign that's not attached to a field
You must specify an item id in parenthesis

When using the above item id instead, I get:

Field sign is not formatted correctly.

I've read the wiki front to back, and I'm 100% certain I'm doing this right. City plot is located within a City Protection field. Server specifics:

MCPC, Essentials, FTB Ultimate.

Any insight would be appreciated.

Has this problem ever been resolved cause I am having the same issue.