In a multi-node environment (Enterprise Terminal Server + Terminal Server Nodes), users get a spinning wheel in the NoMachine client when trying to 'Login as a guest' and the guest account doesn't exist yet on the selected node.

Server log on the ETS host report messages like:
2019-02-15 15:59:21 833.047 80528 NXSERVER WARNING! Cannot send to NXNode. Node stdin was already closed.
2019-02-15 15:59:21 833.133 80528 NXSERVER WARNING! Cannot send logout to the remote node.
2019-02-15 15:59:21 833.503 80528 NXSERVER ERROR! Cannot specify is local node base on: :. (NXNodeExec, /usr/NX/lib/perl/nxserver/NXNodeExec.pm, 2539, NXNodes::isRemoteNode)
2019-02-15 15:59:24 388.810 80612 NXSERVER ERROR! Timeout on session id 'A210CF4A964C0A5E54287241E8CFA560': session was registered 121sec. ago, but it is still in status: Starting

As a workaround, users should close the client and connect again.