"300 seconds left to do another post action."-Probable bug on Wp-Steem Plugin

I got to know about this plug-in called wp-steem which automatically sends our wordpress post to steem blockchain as it says.
In fact, I was searching for the similar kind of tool from a long time. Found this plugin by Hive account@recrypto and wanted to use it on my wordpress blog.

Then I installed the latest version of this plugin on my wordpress blog. Setup the plugin with my steem information(username and private posting key).
But when I finally tried to make a post on my wordpress, I noticed the following alert/notification shown by the plugin.

 Please be reminded that there is a 5 minute cooldown when creating a Steem post in the Steem blockchain.

300 seconds left to do another post action. 

I didn't think it as an error and made a post anyway.

But again I got the same message after successfully made a post.

I checked my steemit profile but didn't found my post there.

I tried whole day posting and deleting articles on my wordpress site but never got it sent to steem blockchain, got the same error message every time.

I have spent lots of time to solve it myself but didn't have any luck. That is why I am reporting this issue as a Bug on Wp-Steem plugin via utopian.

I was using wordpress version 4.7.5 previously. Got this error.
Then I updated to the latest wordpress version 4.9.1. But the issue didn't solve.

Please provide me the solution for this issue if it's not a bug anyway.