add a property to users that was there and got deleted before

add a property to users that was there and got deleted before

Hello,

In zoho crm, I had a field for users that was called 'Firm', and it was deleted, then I currently want to add a 'Firm' field again to the users, but when I try to create it I get a message Duplicate field label found. Enter a unique label. but currently I don't have any field called Firm so what can I do now ?