I haven't seen this issue myself, but I think the problem isn't with the dates you're selecting but perhaps with your Workspace permissions or the attachment space limits on your current plan?

I was thinking it could be permissions. Not sure if I can see my own list of permissions. 

If you open a Workspace, you should see a list of users on the right side. Clicking on one of them should open up the sharing settings for the Workspace and show you everyone's permissions.

(I'm saying this as a Workspace admin, so I'm not 100% sure if this will work for you)