Additional Information
Given the maximum current drive capability of the 9263 (1mA per channel), the minimum external resistance that is needed to generate 10 V is 10 kΩ. Therefore, when the external device contains less than 10 kΩ of resistance, the NI DAQ device will not output it's maximum voltage.
You could optionally switch to using an NI-9269 C Series module. Because it has a smaller output impedance, the threshold at which it will produce 10 V should be covered by most external devices.
You could also design a custom circuit which increases the resistance seen by the module. However, you would need to make sure that this still works for your external device.