I think that the correct translation for that would be something like that :

Tu es difficile à contenter.

Contenter is a 1st group verb (-er verbs, mainly).

There for the conjugation table.

Ou: Tu es (vraiment) difficile à satisfaire.

I think you could put even greater emphasize on the person by omitting any literal (and arguably redundant**) translation of “to please” and just use “difficile” [and even add an object pronoun for extra stress/emphasis, if desired]:=

“Tu es difficile [, toi]!”

**Please note: my parenthetical mention of the possible redundancy of insisting on translating and including the separate notion of “to please” in your French version is based on my (non-native) interpretation of the following part of the CNRTL (TLFi) entry for Difficile, which seems to be saying that the notion of “à contenter” (to please) is already included in contexts such as yours:

DIFFICILE
….

B.− [En parlant d’une pers., d’un animé]

1. Qu’on a peine à contenter.

Il est difficile de te faire plaisir.
Il est difficile de vous faire plaisir.

To please someone = faire plaisir à quelqu’un.

Look, Mummy, no hands [joke, no contenter].

That is the most obvious answer I should think.

Le Robert & Collins Dictionnaire [bilingue]

please (c) plaire, faire plaisir, intransitive

please, transitive (a) plaire à, faire plaisir à, satisfaire, contenter

I did it just to please you: Je ne l’ai fait que pour te faire plaisir.
He is easily pleased/hard to please: Il est facile/difficile à contenter ou satisfaire. So, it is there but so is faire plaisir à.

Lately reading this post, I was sensible to the polemique about @Lambie’s opinion, and I actually had to mind something important that seems to have been totally ignored till now.

As a French native speaker, my own spontaneous translation was the one already cited by @Annie CHABOT:

Tu es difficile à satisfaire

Then reading the whole thread, I easily accepted:

Tu es difficile à contenter

as pretty equivalent, and totally correct (the choice between “satisfaire” and “contenter” being purely matter of literary taste).

So I was surprised to see @Lambie so insisting to claim that it’s totally wrong, while it seemed so obvious for me.
And suddenly I realized that, as he evoked somewhere, we (French native speakers) may be wrong not when choosing this or that idiomatic translation but at the top level of our primary understanding of “please” in the given original English sentence.

The point is that, clearly, for me as well for all other French native speakers, “to please” here is spontaneously understood as something like:

1. to successfully respond to your expectation

(hence the translation “satisfaire” or “contenter”)

But it’s true indeed that another, basic, sense of “to please” is:

2. to do something (or merely to behave in a way) that you’ll like

(then the correct translation is “faire plaisir”)

The (rather subtle but real) difference is that “to please” (or not) means how you’re (or not) glad of either:

1. something you precisely asked for
2. something that you didn’t plan (nor expect) but was done with the intention of being pleasant

I think that the true meaning, in the case of the given original sentence, depends on the interpretation of the context.
And we must simply notice that for some reason the #1 is the more obvious one for us, French native speakers, while perhaps the truth is in #2!

Now it’s up to English native speakers here (notably @Papa Poule, AFAIK, and maybe @Lambie), to let’s know which is the true original meaning, so leading us to a final sure translation.

Tu es difficile à plaire/contenter

Is grammatically correct, but it is much more common to use the impersonal structure:

Il est difficile de te plaire/contenter/faire plaisir

Romain

Descartes’s Discours de la méthode famous first sentence is:

Le bon sens est la chose du monde la mieux partagée : car chacun pense en être si bien pourvu, que ceux même qui sont les plus difficiles à contenter en toute autre chose, n’ont point coutume d’en désirer plus qu’ils en ont.

It has been translated en English to:

Everybody thinks himself so well supplied with common sense that even those most difficult to please. . . never desire more of it than they already have.

“Difficult to please” might be translated by difficile à contenter in literary French.

A word by word translation of “you are difficult to please” would then be:

Tu es difficile à contenter.

This is grammatically correct but arguably less idiomatic than:

C’est difficile de te contenter.

Contenter is however not very common in spoken French. Satisfaire is but I wouldn’t suggest:

C’est difficile de te satisfaire

because it might be risky due to the potential sexual connotations. There is also the simple:

Tu es difficile

This is a very common idiomatic expression, and its most usual meaning is precisely describing someone who is difficult to please:

B.− [En parlant d’une pers., d’un animé]
1. Qu’on a peine à contenter.

There is an issue with tu es difficile though as another meaning of this expression is:

2. Qui, par tempérament est peu agréable à ou pour son entourage. Quel ami quinteux et difficile! il a toujours quelque murmure sous la lèvre (M. de Guérin, Corresp.,1837, p. 297).
   − [P. méton. du subst.] Caractère, humeur, naturel difficile. C’était un homme simple et bienfaisant mais d’humeur changeante et difficile (Guéhenno, Jean-Jacques,1950, p. 42).
   − Spécialement
   ♦ Enfant difficile. Enfant qu’on n’élève pas facilement (cf. aussi Lafon 1963). Synon. indocile, insubordonné; anton. facile, obéissant :

This seems much more negative than “difficult to please”.

Être difficile is nevertheless often used in a positive way like for example this quote, probably inspired by a Churchill one:

Je ne suis pas difficile, je me contente du meilleur.

If for some reason, you don’t want to use tu es difficile, other adjectives might be chosen depending on what context the English sentence need to be translated:

Tu es exigeant (demanding)

Tu es perfectionniste

Tu es pointilleux (picky)