Oncidium hybrids like Sharry Baby "Sweet Fragrance" only have scent when there is sunlight ~ No more scent in the evening and at night ~ That is normal ~
Look at the pseudobulbs of your oncidium. They are much smaller and shorter than the original flower bulbs when you bought in. This means your oncidum is not growing optimally. Main reasons could be insufficient sunlight and root rot ~ Oncidium can still flower even though they are not strong enough. The first thing is to increase light and see whether there is anything wrong with the roots ~