A dehumidifier works in a similar way to an air conditioner, cooling the air that passes through it so water vapour will condense and collect into a container.
If the fans are working and air is circulating through the unit but no water is being collected the internal refrigeration system probably has a fault...
Could be the humidity is low enough it isn't turning on. Try to lower the humidity setting to see if it will turn on. Once the humidity gets down to about 50-55%, dehumidifiers don't work very well at pulling out the humidity..
maybe the new unit is too big for the space. If it is cooling, it is dehumidifying. whenever warm air passes over a cold surface water falls out.
IF, however, it cools too fast, it does not take much water out before it is at temp and shuts down.