"This is your only workspace. Join or create another one first."
You cannot leave your only workspace. Create a new one from the account menu, or accept an invite to another team. Then leave this one. See Work in several workspaces.
The Leave workspace button is greyed out
You are the owner of this workspace, and the owner cannot leave. See If you are the owner.
"You own this workspace — owners cannot leave it."
You are the owner, so OnlyX refused to let you leave. To close the workspace, email support@onlyx.ai.
I left a workspace by mistake
Ask an owner or admin of that workspace to invite you again. When you accept the invite, you are back. They may need to assign your creators again.
"This workspace is suspended. Contact support."
OnlyX has suspended the workspace, so nobody can open it. To ask about it, email support@onlyx.ai.