DIAGNOSIS You're likely using the 'Over Ice' brew type but with the wrong grind size or coffee amount, or the machine's heater is underperforming.
FIX First, ensure you're using the right process. Select OVER ICE. Use the same amount of grounds you would for a hot cup, but use the 'Rich' setting. The machine automatically brews a stronger, smaller volume of hotter coffee designed to melt some ice and chill properly. Always use a coarse grind. Fill your cup with ice first, then brew directly over it.
IF THAT DIDN'T WORK The heating element may be scaled up. If your hot coffee also isn't as hot, run a descaling cycle (vinegar/water mix) to restore heating efficiency. Mineral buildup acts as an insulator.
HEADS UP The 'Over Ice' setting brews at a higher temperature than the standard hot setting. If it's truly brewing lukewarm on all settings, that's a heater failure and requires service.