There are numerous reasons why an air cooler would fail to cool certain CPUs.
• The first thing to check is that the the cooler's stated TDP can handle the CPU at boost levels; CPU manufacturers state TDP at PL1 (pre boost) levels. TDP may not be the most accurate way of rating cooling capability, but it is the easiest metric to apply.
• A user can also try reseating the cooler on the CPU with fresh thermal paste, while making sure that even pressure is applied during installation.
• Also, check that the fan(s) are plugged into the CPU_Fan header.
• The last piece of advice is to double check that the protective sticker on the cold plate is removed; it is very common for someone to forget to remove the sticker while installing coolers.