Premiere Pro 2020 起動するとワークスペースエラー

are you on a mac or a pc?  I can speak with some authority regarding macs and I imagine the same principles apply to windows.  Modern computers can have multple users and each user has varying degress of access to material on any hard drives available.  If you select a folder or file on the mac and "get info" and scroll down to sharing and permissions, you'll see how can access that folder/file and what are their "privileges."  You can add a user and change the privileges and once you do that you can apply those changes to folders and files within that folder by clicking on the gear wheel below and choosing "apply to enclosed items."  In particular, updating your operating system or bringing a drive in that was used on another computer can cause problems with permissions.

If I remember correctly (and hopefully someone else will correct me if I'm wrong) the workspaces are stored in your documents folder.  You should see an adobe folder and within that a premiere folder with folders for the various versions of premiere installed on your system.  I don't think the workspaces are saved with a name that seems obvious, but explore those folders and check permissions and make sure you have read/write access to them.  

If any of this is not clear, post back.  You might also search in this forum for "permissions" and you might find a better explanation

Good luck