ovftool Export Fails with vim.fault.InvalidState in Maintenance Mode

On VMware ESXi, I tried to back up a guest OS inside the ESXi server to OVF from a client.

VMware OVF Toolを利用してESXi 6.7からVMをエクスポート - redj’s blog (in Japanese) I used that detailed article as a reference. (Thanks)

When I stopped the guest OS and tried the backup, an error occurred

# ofvtool vi://[username]:[password]@[ESXi IP or FQDN]/[inventory name] [output OVF name].ovf

Error: Fault cause: vim.fault.InvalidState

With backups on the older Vsphere you had to switch to maintenance mode, and the cause was that I had done exactly that.

It seems it cannot be done while in maintenance mode.