How to use NE_AUTH_WEAK_DIGEST?

I'm trying to connect to a WebDAV server built-in to an iPhone app (FileBrowser to be specific), but I keep getting the following message:

Could not authenticate to server: legacy Digest challenge not supported
Connection failed.

I've read online that I can either use this (NE_AUTH_WEAK_DIGEST) flag or use an older version of WinSCP.
Any help in being able to connect would be greatly appreciated. Thanks.

You cannot "use NE_AUTH_WEAK_DIGEST". That's something WinSCP code would have to use.
You can vote for it here:
Issue 2109 – Restore support for legacy version of the Digest algorithm specified in RFC 2069