Can't edit Workspace settings or access

Hi, I hope there's a simple solution to this that I'm missing;

I created a few workspaces a while back & had the ability to edit the settings & access on all 3
I've been working away on my first dashboard of any significance, which I'm publishing to 1 of those workspaces and am now ready to roll out to our Sales Team
But when I click on that workspace, "Workspace Settings" are only available to view, and the 'Access' button is not visible at all

I had already given 3 users "Workspace Viewer" permissions to this workspace, but now am unable to add any more users to this role
During the development of the dashboard in this workspace, I created an App, I've since deleted that app, & now there is no longer the button to "Create App" in this workspace either
I'm thinknig this is probably related as I came across a forum saying that you could manage access in the App, but I no longer have an app for this workspace

Any pointers would be appreciated