Few weeks ago, Forgerock has released OpenIDM 2.1.0 and i noticed a little "sneaky" change in the way of calling a reconciliation through REST. In the previous version we used to do so as follows :

$ curl header "X-OpenIDM-Username: openidm-admin" header "X-OpenIDM-Password: openidm-admin" request POST "http://localhost:8080/openidm/sync?_action=recon&mapping=systemXmlfileAccounts_managedUser

And now on :

$ curl header "X-OpenIDM-Username: openidm-admin" header "X-OpenIDM-Password: openidm-admin" request POST "http://localhost:8080/openidm/recon?_action=recon&mapping=systemXmlfileAccounts_managedUser"

The only difference is the "sync" and "recon" words in the URIs. So if you are migrating from a previous version make sure you don't call the REST api the old way because It can be tricky to debug this misuse.