The plugin does not have a valid header.

I have the same problem. They told me in my own support thread to try one of the basic themes (twenty sixteen) and if that doesn’t work then try turning off plugins and seeing if any of them are causing it.

Personally I don’t need this plugin, I just wanted to see if I could have some extra security. I’m not gonna go through all that trouble and mess up my store for a few hours, but if you have a small site then you could give it a try.

I am having the same issue.

Just tried for the 3rd time and it did activate this time.

I have no idea what is causing this issue.

KonaGirl, that was my fault, sorry about that. For some reason there was an extra folder with another copy of the plugin inside of it. I just deleted that folder and that error should be completely gone now. Sorry for the hassle and sorry for not seeing this until now.

Thanks for letting us know, Nick. Appreciate it!