The infuser cooled down between uses. Warm it by pressing the rinse button before making coffee. Also, your cups are cold. Rinse them with hot water using the machine's hot water function first.
If the coffee is still lukewarm, check the temperature setting. It has three levels. Turn the selection dial to the coffee cup icon, then press the 1-cup or 2-cup button to cycle through the temperature settings until the desired one lights up.
For consistently hotter coffee, run a rinse cycle into your cup right before brewing to warm everything up.