It seems one of the Forest licenses in your server has not been updated correctly. Please, do this:
1) Open Forest in your PC to reproduce the error.
2) Open the License Manager from your server, and see the log clicking License Server->View Log.
3) Find the last entry where the license is assigned the IP address of your computer, such as this:
22/04/2016 09:05:21 I Sending license 1234567890 to 192.168.1.2
4) Find that license in the server, and activate it again using the code your received with the renewal.
Note: it's possible that you receive the error in other PC, because licenses are assigned randomly. If so, just repeat the process with the right IP address.