logic level conversions for opto-isolators in digital input acquisition
Your NI-6525 device needs your driver to be able to source up to 3 mA current. 
However, the MAX3000E is specified only for 20 µA (see VOHx); a bidirectional level shifter with automatic direction sensing must have weak outputs to allow another device to override the voltage level.

To get stronger outputs, use a unidirectional or direction-controlled level shifter, such as the (SN)74LVC2T45.