Seafile on mounted partition: operation not permitted

I'm not sure whether this is more a problem with Seafile or Ubuntu so I will just ask here:

I would like to sync Seafile to a folder on a mounted partition called 'data' mounted to /mnt/data. Thats because I am using dualboot with Windows 10 and want to avoid to download the same files twice. So instead I have a exFAT partition both Ubuntu and Windows 10 can access.To mount this partition I am using the following entry in /etc/fstab:

/dev/disk/by-uuid/4B27-57D4 /mnt/data auto nosuid,rw,user,nodev,nofail,x-gvfs-show,uid=myusername,gid=myusername,umask=000 0 0

Everything works as I should so far. The partition is mounted automatically on start up, I got full access, permissions etc.. But when I try to setup Seafile to use /mnt/data/Seafile I get the following error message:

failed to bind unix socket fd to /mnt/data/Seafile/.seafile-data/seafile.sock : Operation not permittedseaf-daemon.c(527): Failed to start searpc server.

Why is the operation not permitted? Is there a permission I haven't setup yet? Or might this problem just be related to Seafile?