Please unzip your exported file and check that your exported zip file contains a settings.json file and uploads folder with images. Sometimes the export process is prematurely terminated by server due to exceeding max_execution_time.
Also check that your export file size in smaller than the post_max_size and upload_max_filesize setting on your server, also the max_execution_time may need to be increased so that it completes it’s unzipping and importing process on server. post_max_size and upload_max_filesize are PHP values, which ca be viewed in PHP info, using the following plugin. https://wordpress.org/plugins/wordpress-php-info/
Sorry, that’s all I know on this issue.
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