Is it necessary to pay zakat again if the poor person was not informed that it was zakat, especially after the daughter got married and what was bought as zakat moved to the marital home?

It is not obligatory to inform the poor person that the money given to him is zakat (definition); rather, it is preferable not to inform him, and this is the view of the majority of scholars. However, if it is known from the situation of the zakat recipient that he does not accept zakat, then informing him becomes obligatory so that he is fully aware. As for giving zakat as a monetary value, there is a difference of opinion. If it is held that monetary value suffices, then your zakat would be valid if your uncle was unable to prepare his daughter for marriage and the zakat was for that purpose. Otherwise, you must give the zakat again.