If you're behind a proxy and want to use Zeplin's Photoshop plugin, open a text editor and enter the following lines as necessary:
HTTP_PROXY=http://your proxy address
PROXY_USER=your username (This line is optional.)
PROXY_PASS=your password (This line is optional.)
Name the file plugin.env
and save it to <Your Photoshop folder>\Plug-ins\Generator\io.zeplin.photoshop-plugin
then restart Photoshop.