I am also having the same issue however I'm having no luck with the above solutions. My shared folder is already Windows ACL formatted.
What are you guys using for the address when you set up WebDAV sync? I know Enpass is really picky on formatting and I'm curious if I need to be changing something in my address.
Maybe not any help for you , but for me it works with internal address of my Synology : http://192.168.0.x:5005/enpass/
Externally it still doesn't work : https://xx.synology.me:5006/enpass/ --> here I get error "could not connect to specified WEBDAV folder. Check your username and password"
Webdav on Synology Nas
in Enpass Support & Troubleshooting
Posted
Maybe not any help for you , but for me it works with internal address of my Synology : http://192.168.0.x:5005/enpass/
Externally it still doesn't work : https://xx.synology.me:5006/enpass/ --> here I get error "could not connect to specified WEBDAV folder. Check your username and password"