Seurat define manually a cluster and find markers
It would have been better if you have shared your code as well as the error messages you got format these as such.

As far as I can understand, your problem is that you failed to make your cluster as default ids. For this you can use:

seurat_obj &lt;- SetIdent(seurat_obj, id=seurat_obj@meta.data$column_of_interest).


The cluster identities are stored in the @meta.data slot of your object.