I have an update.
if I right click in the Obj Navigator and select Generate I am told:
plsqldev
could not generate documentation for DEPT
ORA-01012: not logged on
Process ID: xxxx
Session ID: xxx Serial Number: xxx
(Generate Table)
So I thought it might just be possible that I was inactive long enough so I did a Session / Logoff / All and logged back on.
I got the same error. According to the Window title I am connected, the Command Window status are agrees and I can issue DML in the Command window and it returns data.
I closed PLSD and restarted it. in Obj Nav I hi-lighted all the tables that start with 'A', right clicked, selected Generate and it is running along fine.