Colin,
Plaire is one of the ‘ difficult ‘ verbs in French that seem to ‘work in reverse’ in this situation, coming from an English speaking perspective. Manquer is another prime example. There are others, but getting the hang of these 2 common examples is worth the effort.
The verb structure here is actually ‘ plaire à qqn ‘. In the common expression you quote, the impersonal pronoun ‘il’ is the subject of ‘plaire’.
You cannot follow it with the subject pronoun ‘tu’. An indirect object pronoun is needed, representing the person or people being addressed and not the speaker.
When addressing an individual informally that is ‘ te ‘, as in this case. By the same reasoning, in formal language it would ‘ s’il vous plaît ‘.
I suspect that like many of us, you will need to read through the linked lessons more than once, and I recommend reading their QandA as well for some great tips and previous responses to similar questions.
Expressing you like something/someone in French with the verb "plaire"
Using manquer (à) to say you miss someone or something emotionally in French
