Google webmaster is blocking links due to robot.txt in wordpress

I just completed my wordpress website and added it to the Google Webmasters. Verification is done succcessfully and the robot.txt is also submitted in webmasters.

I am using “yoast seo” pluigin to setup the SEO part. So, I am using their sitemap as of now. But, when I test the sitemap whose path is domain/sitemap_index.xml the google webmaster is giving this error “Url blocked by robots.txt” and there are total 23 URL’s blocked by google.

I have done following things to rectify the possible issues:

1. The “discourage search engines” option is not checked.

2. I have installed a plugin to edit the default robots.txt and my current robots.txt is below:

User-Agent: *

Disallow:

3. I have also checked .htaccess file and it is looking fine.

I am completely clueless about this issue and how to resolve it. I have deleted my website from webmasters 7-8 hours back and added new link without www. I haven’t submitted the sitemap till now because I hope that I will be able to get some guidance before submission so that this time there will be no error. I still do the test run by giving the sitemap path, but it comes with the same error of link blocking.

Looking forward to some help..