Have the same problem. WebDav is selected. SMB connection with the same credentials is working.
Log says :
kantoor.domain.nl - - [10/Nov/2015:22:22:11 +0100] "OPTIONS /webdav/sharepoint/ HTTP/1.1" 401 456 "-" "WebDAVLib/1.3"
kantoor.domain.nl - user [10/Nov/2015:22:22:11 +0100] "OPTIONS /webdav/sharepoint/ HTTP/1.1" 401 456 "-" "WebDAVLib/1.3"
kantoor.domain.nl - - [10/Nov/2015:22:22:18 +0100] "OPTIONS /webdav/sharepoint/ HTTP/1.1" 401 456 "-" "WebDAVLib/1.3"
kantoor.domain.nl - user [10/Nov/2015:22:22:18 +0100] "OPTIONS /webdav/sharepoint/ HTTP/1.1" 401 456 "-" "WebDAVLib/1.3"
default 127.0.0.1 - - [10/Nov/2015:22:22:29 +0100] "OPTIONS * HTTP/1.0" 200 - "-" "Apache/2.4.16 (Unix) OpenSSL/0.9.8zg PHP/5.5.29 (internal dummy connection)"
default 127.0.0.1 - - [10/Nov/2015:22:22:30 +0100] "OPTIONS * HTTP/1.0" 200 - "-" "Apache/2.4.16 (Unix) OpenSSL/0.9.8zg PHP/5.5.29 (internal dummy connection)"
default 127.0.0.1 - - [10/Nov/2015:22:22:35 +0100] "OPTIONS * HTTP/1.0" 200 - "-" "Apache/2.4.16 (Unix) OpenSSL/0.9.8zg PHP/5.5.29 (internal dummy connection)"
default 127.0.0.1 - - [10/Nov/2015:22:22:36 +0100] "OPTIONS * HTTP/1.0" 200 - "-" "Apache/2.4.16 (Unix) OpenSSL/0.9.8zg PHP/5.5.29 (internal dummy connection)"