There are several factors why your unit isn’t cooling your space. Before all, ensure your unit has the recommended BTU for your room. This calculation isn’t only based on area but also on room orientation and room function. South-facing rooms with prolonged direct sunlight will need a higher BTU than shadier rooms. Similarly, rooms containing more people will need greater AC power. Energy Star has a helpful BTU guide.
Another consideration is poor insulation. Open plan spaces, open doorways or other ventilation will decrease your air conditioner’s efficacy. See if you can seal up poor insulation or hang up partitions in open plan spaces.
Also, bear in mind that even a powerful machine will have a harder time performing during extremely hot weather. If you are experiencing a heatwave, and your unit isn’t cooling as well as it used to, then you may need to wait it out and see if it resolves once the intense heat and humidity subside.
Still not cooling? Contact customer support.