pg96 not running as service

Hi All,
System:Win server 2016
Version:pg9.6

I have had an odd problem happen today. My server that has been running
fine for 2 years has decided that it will not start any more. Investigating
a little i have found that it works fine when running from command line,
using either of the below commands:

C:\POSTGR~1\pg96\..\pg96\bin\pg_ctl start -c -w --log "C:\tmp\logs.txt" -D
"C:\PostgreSQL\data\pg96"

C:\PostgreSQL\pg96\pgservice.exe "//TS//PostgreSQL 9.6 Server"

but when trying to run as a service (using
C:\PostgreSQL\pg96\pgservice.exe "//RS//PostgreSQL 9.6 Server") as system
user i get this in the windows event viewer
pg_ctl: could not start server
Examine the log output.

I have looked at the logs, both in C:\tmp\logs.txt (empty file) and
C:\PostgreSQL\data\logs\pg96
(no new lines) no no avail. Can anyone help me out??

This seems to happen soon after I created a new DB using pgadmin4 and had a
new instance of bitbucket populate it, but not immediately after.

Thanks for your help!

Peter