GL foreign currency revaluation

Hello,

We´re trying to perform a foreign currency revaluation in the General ledger which we have done before but it doesn't work for  a particular month. We use Microsoft Dynamics AX 2012 R2.

We have run the revaluation for October 2017 however it has not worked for November. I have recreated this in the test environment and but I cannot resolve the issue. There is nothing obvious that has changed in the set up since October. I have also tested the revaluation for December and this works fine.

Any ideas and suggestions