You can't do that. What you actually sent to the SQL server was this:
SELECT * FROM Project WHERE ProjectID IN ("'PFP', 'PSB', 'PSK'")
You didn't send a list of items, you sent a single string. Essentially the same as sending
... WHERE ProjectID IN ('I SENT THIS SINGLE, STRING NOT A LIST')
You can't directly send a list to SQL Server in the IN clause. Read this
] for a possible alternate method.