Can you send the error log to me? Without detailed information it's hard to find out the cause.
You don't need to uninstall FB4.6 if you already have one installed. In that case the EB2.1 will be installed right in that FB you already have.
A total uninstall/re-install of FB 4.6 and EB 2.1 solved it.
It is much more important to us that you responde to my previous post about .ZXPs not being produced by the export wizard.