If you are seeing this error it can mean one of many possible reasons, most likely it is nothing to worry about
First, login to WHM and click ‘Details’ next to “The last attempt to update cPanel & WHM was blocked”. A small popup window will explain what the issue is.
Here’s one of the possible reasons:
“Please correct these issues and rerun updates.
info: Upgrade to the next LTS is blocked until Monday Jun 22, 2015 in order to distribute upgrades over a five day period. If you wish to upgrade now, you can do so now with the force option.”
When cPanel releases major updates, it spreads out the distribution over a period of time to avoid everyone from updating at the same time which would result in overloading their servers. So don’t worry, just wait until the date shown for it to automatically complete the update. If for any reason you want to upgrade right now, you can simply login to ssh and type the following to force it to update now: