What is the ruling on demanding that a partner who has not fulfilled his obligation in a company refund the amounts paid by the other partner on his behalf, and is what he is doing considered an injustice?

The partnership between you is one of labor and capital, and it is permissible شرعًا (Islamically). If one partner works without the other, that does not nullify the share of the one who did not work, and the profit remains divided between them according to the agreement as long as the partnership contract is valid. If you paid the rent for the premises alone with the intention of claiming it back from your partner, then you have the right to demand it. The two partners must reach an understanding to resolve problems, otherwise, the Sharia (definition) courts are the arbiter.