For example, these IDs don't convert using biomart:
ENSG00000284928 ENSG00000284930 ENSG00000284931 ENSG00000284932 ENSG00000284934 ENSG00000284946 ENSG00000284948 ENSG00000284951 ENSG00000284952 ENSG00000284954 ENSG00000284956 ENSG00000284957 ENSG00000284959 ENSG00000284962 ENSG00000284964 ENSG00000284966 ENSG00000284968 ENSG00000284969 ENSG00000284976 ENSG00000284977
This is a frequently asked question with multiple prior threads:
How to use biomart on R to convert Ensembl Gene IDs to Symbols?
Question: Convert Ensembl Transcript Ids Ensmust To Gene Symbol In R
converting mouse emsembl gene IDs to Gene names by bioMart and gconvert with no luck