Did you modify the following options in the
/opt/bitnami/php/etc/php.ini file to increase the allowed size for uploads?
; Maximum size of POST data that PHP will accept.
post_max_size = 16M
; Maximum allowed size for uploaded files.
upload_max_filesize = 16M
The, restart the servers for the changes to take effect.
sudo /opt/bitnami/ctlscript.sh restart
What method are you using in order to upload the file? We have a guide about how to upload files using SFTP, just in case it helps: https://docs.bitnami.com/google/apps/wordpress/administration/upload-files/
Carlos R. Hernández