Recently I have patched my lab environment from 6.7U1 to 6.7U2 and have seen issues related to vSphere HTML client loading. Post patching and rebooting the vCenter, it does not load and shows hour glass.
However, tried to login webclient and able to login successfully. I am able to see all the inventory objects in the webclient.
Then, I realized to check vsphere-ui service which is running as expected. I tried to check in another browser and HTML client page appeared successfully. I was able to login.
Most of the people will see this issue in Safari and Mozilla Firefox not sure why but after deleting cache & cookies you will be able to login on same browser too.
Also, there are also few recent tasks related to plugin as shown below:
Incompatible. This is a vSphere Web Client (Flash) only plugin indicated by the missing type=”html” plugin manifest attribute.
When I searched around and found it has been already in notice and post is already in place with VMTN communities link here https://communities.vmware.com/thread/609452
It seems that webclient plugin in HTML client shows incompatible and it is logging in the recent tasks as per above.
So, when you login to HTML client, deploy package failed message would appear in recent tasks which error message. Hence, this message can be ignored.
I hope this post in informative.