I'm having an issue with old NYC transactions.  I've been looking back in our pool's transaction history, and none of our transactions before October 2017 are found in the client.  I'm sure they were valid at the time, but now when I call 'gettransaction' in the client, only the transactions since October 2017 return as valid; the older ones are not found.  I've tried in the block explorer have the same results.  Why would old transactions not show up?  Is this a different chain than the one that was on Bleutrade least year?