I have mouse gene data but I am unable to do conversion through this code:

 # Load required libraries
    library(biomaRt)

    # Read the gene expression data
    expression_data <- read.delim("combined_expression.tsv", header = TRUE, sep = "\t")

    # Extract Ensembl IDs from the first column
    ensembl_ids <- expression_data[, 1]  # Assuming the first column contains Ensembl IDs

    # Use biomaRt to map Ensembl IDs to gene names
    mart <- useMart("ensembl", dataset = "mmusculus_gene_ensembl")

    # Get gene names corresponding to Ensembl IDs
    annotation <- getBM(attributes = c("ensembl_gene_id", "external_gene_name"),
                        filters = "ensembl_gene_id",
                        values = ensembl_ids,
                        mart = mart)

    # Merge the annotation with the expression data
    # Match annotation based on Ensembl IDs
    annotated_data <- merge(annotation, expression_data, by.x = "ensembl_gene_id", by.y = colnames(expression_data)[1], all.y = TRUE)

    # Save the updated expression data as a CSV file
    write.csv(annotated_data, "updated_expression_data.csv", row.names = FALSE)

    # Print a message indicating completion
    print("Gene names successfully mapped and saved to updated_expression_data.csv.")

But its showing NA in external gene id column in updated csv file

I again tried with 10 enseml ids like:

test_ids <- head(ensembl_ids, 10)
test_annotation <- getBM(attributes = c("ensembl_gene_id", "external_gene_name"),
                         filters = "ensembl_gene_id",
                         values = test_ids,
                         mart = mart)
print(test_annotation)

But its showing:

ensembl_gene_id    external_gene_name
<0 rows> (or 0-length row.names)