Subject: bug#31079: Windows - Emacs-25.3.1 Can't find source.tex file

From: [email-masked]
Date: Sat, 7 Apr 2018 18:40:53 +0200

Mmm... From the use of ":" as path separator, and the fact that "/cygwin/" is omitted, it almost looks like AUCTeX is seeing your machine as a Linux one...

If you issue "C-h v system-configuration", what value do you get?