I recently setup WordPress using Synology Diskstation and all seemed to go well until I tried to change the permalinks. Wordpress reported that the htaccess file was not writeable and the resulting nicely formatted url links simply gave a 404 page error. The fix was quite simple, on the diskstation, open web station and change the server from “Nginx” to “Apache HTTP Server 2.2” You also have to do this for any virtual servers you have set up. Viola, now nicely formatted links work again.
If you wish to keep Nginx then the alternative method is to use terminal and ssh in as root and change the folder ownership with “chown -R nobody:nobody /volume1/web/wordpress”