Hello.
If you look in the manual there is a specific command you need to issue for aircraft that wish to do circuits.
CLEARED TO TOUCH
AND GO............................................CTRL O
may be followed by RUNWAY XX (for
airports with a multiple runways the L, R
or C designation must be used)
CLEARED FOR STOP
AND GO............................................CTRL T
may be followed by RUNWAY XX (for
airports with a multiple runways the L, R
or C designation must be used)
CLEARED FOR LOW
APPROACH......................................CTRL S
may be followed by RUNWAY XX (for
airports with a multiple runways the L, R
or C designation must be used)
ATC Suite
LEFT CLOSED TRAFFIC
APPROVED CLEARED
FOR TAKEOFF.................................CTRL 8
RIGHT CLOSED TRAFFIC
APPROVED CLEARED
FOR TAKEOFF.................................CTRL 9
This is on page 36 and 37 of the manual.
The planes you are trying to control want to fly in the circuit so will remain in the aerodrome vicinity.
Hope this helps.
Yves