Hey,
I’ve been contacted about this problem before and its confuzzling me, to be honest. I tried to find solutions and made sure I had a valid header but its still saying invalid.
However, while I search for a solution ?? I recommend people activating this plugin through the plugins menu, instead of activating it once the plugin is installed. For example, when you download the plugin and it says finished download it gives you an option to activate the plugin? Don’t activate it, instead, back out or simply go to the plugins menu in the dashboard and activate it through there. It works fine when you do that, its a weird bug :/
Also, this only seems to happen when you use the wordpress directory to download the plugin so maybe its something to do with the SVN. I’ll look into it, in the meanwhile like I said, users can activate the plugin through the plugins menu or by using ftp upload.
