Sometimes your upload may stop progressing with only one image left (ie. 39 of 40). Although Google Chrome is Ambra's preferred browser, this is an issue that can sometimes arise during uploads (most often with CT scans) due to the way that Google Chrome processes the image syntax.
If this is the case, please try uploading using Mozilla Firefox instead. You can download Mozilla Firefox here.
More information about Ambra's compatibility with different internet browsers can be found here.
If you are still unsuccessful, please submit a ticket request here.