Database is not registering with listener.

Oracle 21.3.0.0.0 XE on Windows 2016.

We use XE for certain small applications and on one computer (VM) the XE DB has stopped registering with the listener. There is only one DB and one listener on this server.

When running

lsnrctl status

It does not show either the CDB or the PDB.

The listener.ora and tnsnames.ora seem to be OK. I can connect to the DB using;

sqlplus / as sysdba

The database seems to be fully up and the PDB seems to be mounted read/write.

In reviewing the listener log I can't see anything amiss, I don't see anything in the DB alert.log.