WP Maintenance error after updating

Hello,

I am using the wp maintenance plugin after upgrading to the version 3.0 today I was facing a 500 Internal server error to my admin side of the installation. I have de activated the plugin and everything is ok again. But I think that there is a bug in this version. I am using wordpress 4.6.4 with salient theme. If anyone can help me resolve this issue it would be great because this is a great plugin and I would like to use it again.