There is a filter in Database | Monitor | Session Browser that runs the following query:
select * from v$session s
where
(
program = 'frmweb.exe'
)
This select returns rows in the SQL Editor but the filter does not return anything.
These users are SYSTEM users and the SYSTEM users are excluded in the filter.
RESOLUTION
Please click on the arrow next the filter icon and uncheck 'Exclude NULL and SYSTEM OS Users'
