A technical message from your browser telling you “the request entity is too large” or “content length exceeds the configured value” means that the size of your import file exceeds the maximum allowed file size. Files around the 28MB size or higher may result in this type of message and stop an import file upload.
A work around for this scenario is to split up your import into multiple, smaller files each with less rows and/or columns of data. Divide the data up into smaller files and import each file separately.