Niche is a quite big site to import, I assume something from your server is stopping the importing.
The following server settings can be increased to better allow GP to upload and process the import files:
upload_max_filesize (256M)
max_input_time (300)
memory_limit (256M)
max_execution_time (300)
post_max_size (512M)
If you’re not comfortable tweaking these yourself, your hosting support should be able to help you.