We’ve encountered problems with several customers that when one initiates removal of clients this does not seem to be executed pretty soon as expected.
Furthermore clients that are never getting online again and that shall be removed can’t be removed since the second step of removal within the Hub can’t be accessed. It is just graed out…
Must be a bug comming from one of the last Hub updates.
Confirmed. The issue is here since the last update 8.67.
We have a support ticket about this issue.
No news from AVAST 
From AVAST:
I’m contacting you from our Tier 3 Avast Business Technical Support team to let you know that we are aware of this issue, and that at this moment we do have a workaround for it:
You can select other devices that are in Installed status, and then also select the uninstalling devices, the remove and uninstall will work.
If you don’t want to remove any device that is in Installed status, but you still need to remove one or more devices now, you can install some device with the Business Agent only to uninstall it after as per workaround above.
I hope this helps for the moment, however your Support case was linked to the mentioned known issue, and you will be notified about the progress and/or the once this will be resolved by our development.
It seems that AVAST has lanched a fix fot this issue.
Working now! :o