I had the same issue on another system that I setup today. Both installs are using version 4.0.0. I even tried deleting the snmp data source and then add it again from scratch. When I check the data point values in the data source tab all the snmp points are reading data fine. when I open each data point it shows a XID associated with the data point. However when I am in my dashboard editor and I try to assign the XID to things on my dashboard the data source XID's are not in the list. I also tried copying the XID and pasting it into the field on the dashboard. I have other devices that appear in the XID list just fine. Is there anyway to refresh the list of available XID's in the dashboard editor.
Below is screenshot of the dashboard editor. The data point XID shows all the points from my Moxa switch. However the other device just not show in this list.
This screenshot shows my data source and all the points are reading and are valid.