Without commenting specifically on the machine or the seller, it could be many reasons as to why a clear coat has gone 'cloudy'.

Firstly I would check whether it was a 2k (2pac) clear or a one pac clear.

If its 2k, it may be due to incorrect mixture of hardner / clear / thinners.  Incompatible products, moisture in the airlines / gun or many many other possibilities.

If it has been rubbed back (say to 3000 grit) and not polished correctly it may be a reason for cloudyness.

Realistically to repair, the playfield would need to be fully stripped and sent off to an expert like El Timbo for inspection.  He would be able to tell you if the problem clear can be rubbed back and redone, or if it just needs to be polished correctly with a kit.