The house has been rented out and the landlord wants to sell it. Does the intermediary have the right to show the client the house every day?

Yes, it only involves that you still live in the property, so you have the right to negotiate with the owner and agree on a unified viewing time. Because the previous lease contract was signed by you and the owner, and the real estate contract was signed by the owner and the intermediary company. You have nothing to do with the agreement between the intermediary company and the owner. The intermediary can take people to see it, and because you have paid the rent, this way of selling houses has interfered with your normal life. You can negotiate with the owner to solve it.