There could be two problems. See KB1062 related article
In LNS mode, if you crreated the scheduler functional blocks in OpenLNS CT and dynamically created a netework variable to schedule, the scheduler application may not correctly reference the variable as a datapoint to write values to. You should make sure the smart server is synchronised to the LNS database and that the scheduler functional block appears under the iLONApp Device and the variable you created in the Visio drawing appears underneath scheduler functional block as a datapoint.
Make sure that you select the right hand icon to reference the datapoint. If the list is blank then go back to the datapoint in the left hand tree view and click the datapoint underneath the Scheduler functional block