The commit https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=0a73481226e17813598f9bd19388a1108242ab08 removed screen-4.3.1-r1.ebuild with it files and with screen-4.4.0 I cannot access my screens anymore.
There is incompatibility between the version. See reply to my question: http://lists.gnu.org/archive/html/screen-users/2017-04/msg00000.html
yes there is incompatibility between those versions, from release message (http://lists.gnu.org/archive/html/screen-devel/2016-06/msg00000.html)
"Do note that there was fix to screen message structure field
responsible for $TERM handling, which makes it impossible to attach to
older versions (hence minor version bump)."
You can try to attach by using /proc/$SCREENPID/exe -x
Provided the locations are being shuffled in versions and affected by configure options (see bug #591772) I propose restoring the ebuild. Seems current ebuilds anyway store teh sockets elsewhere.
Moreover, the socket directories mentioned in https://wiki.gentoo.org/wiki/Screen are not those used by current screen installations in Gentoo. Please cleanup the docs, document which version used what. I would appreciate clear einfo message warning about the issues (different socket dirs, incompatibility).