past participe agreement

Question

Why is it vous êtes entré (dans la salle de bain) without an s on 'entré'?

Maarten Kamp · Accepted Answer

Simon, 
the past participle and adjectival agreements with the subject pronoun ‘ vous ‘ accord with the gender and number of “ the subject “, when agreement is indicated per the usual rules of agreement. 
In the sentence you cite, the subject being spoken to is a ( one ) man, addressed politely with ‘ vous ‘.
https://www.lawlessfrench.com/grammar/agreement-with-vous/

Céline Pickard · Answer

Bonjour Simon,
Maarten is correct! Take a look here too:
Saying "tu" or "vous"? That is the question...
Using Tu and Vous to express three types of you in French (French Subject Pronouns)
I hope this is helpful.
Bonne journée !