K2 Blackpearl 4.7 Error: Invalid Archive Type while opening Workspace

Is this a fresh install of 4.7, or an upgraded server? That error often means that one component of blackpearl has a different version than the others

Upgraded from 4.6.11 to 4.7

Try running the configuration analysis tool and see if it can spot (and repair) the issue

Just ran Configuration Analysis and all green

Wil be restoring the VM and DB to last good configuration post 4.7 upgrade to see if that will help. Will post the update shortly

You might also see that if you upgraded the server but not the client tools like K2 Studio or Visual Studio.

Here is what it shows in Control panel:

After successfuly K2 VM and K2 DB restore to last known good configuration, I was able to get to fully functional K2 4.7 and also was able to update to K2 5.1.

This may not apply but I was going to upgrade to 4.7 and wanted to get the 5.1 system key.  I started the installation wizard  and got the key and canceled.  However, I found when I went to the 4.7 workspace that I got the same (or similar) error.  Any chance you did the same?

Sorry that had to be so painful, I'm very curious as to what the underlying problem was but I'm glad you are up and running!

Not entirely sure. Though, I just upgraded the Dev with Fix Pack 13 which is August Release and everything is up and running now.

No wasn't the case

Do you have the full stack trace for the error? When you see the error in workspace, is there a button that allows you to see more details?

You can also try enabling full host server logging, then open your workspace again. Once the error appear, check your latest HostServer log if there is the same error message being logged. Paste the full stack trace if you can find it.