cannot install CC Pro version

Just purchased CCleaner, downloaded the product and clicked to install - message stated, this app can't run on your PC...

Yet, the free version does with no issues.

You have 48 hours to rectify or I will contact the Credit Card company and report Piriform as a corrupt business...

No need to report as anything. You can copy paste the registration key you were given into the free and you'll have your pro.