Where is the central locking unit .

check and manually move linkage to unlock ---use a long screwdriver to move lock mechanism or if unlocked move latch to release

Central locking motor for the boot latch may be stuck open. If it also use cable type release, that lever may be stuck at release position.

Got the right button?
The boot latch may be a separate button on the remote.

Failing that check the tailgate lock relay (K24f) - temp swap with K24d (deadlock relay) should work.

If that is not it, it may be a defective microswitch on the tailgate handle.

This is detective work.first place to check is the master unit which can fail due to clogged filter or water ingress.usually found in side boot panel area.if this checks okay.then you need to check each door panel lock to see if air pressure activates lock.you can do this with a syringe body into tube connector of any door and suck or blow air into the tube system.this will reactivate a stuck lock .usually means one or more door cards has to come off.did this on a merc only one door and it fixed the central lock back to working order.

If there isn't an emergency "lock knackered" panel in the tailgate trim, you will probably have to force the trim panel off. These are usually only fastened by plastic pop studs, so you should be able to do it without damaging the panel, although you may need to get replacement studs.

When the tailgate is fully closed, is it actually properly latched down? Try pushing down firmly on the tailgate when it's closed just to be certain as it's possible that the latch is sitting half open at the moment.

Check the wiring between the bootlid/tailgate and the car body could well be there's a wire broken, if so just solder the 2 parts of the wire back together and insulate

According to WIS, the remote boot release is directly connected to the PSE via CAN
The pneumatic system equipment makes vacuum or pressure available for the following systems:Central locking (CL), (pressure, vacuum)Remote trunk release (RTR), (pressure)- actuation via remote trunk release switch or via radio
AD80.20-P-2002-02B Remote trunk release, general notes on Models 202.01/02/12/12 as of 1.6.97,diagnosis, advanced information, RTR 208, 210 as of 1.3.97, 210.081Actuation of PSE control module:The remote trunk release switch (N72s15) is connected to the PSE control module (combined) (A37) via CAN data buses. The remote trunk release radio signal from the key is conveyed to the overhead control panel control module (N70) via theantenna. This transmits the signal to the electronic ignition switch control module (N73) via CAN data buses. If a valid signal is recognized there the PSE control module (combined) (A37) is actuated via CAN data buses. The remote trunk release IR signal from the key is conveyed to the respective door control module (N69/1, N69/2) via the IR receivers (A26/1, A26/2). This transmits the signal to the electronic ignition switch control module (N73) via CAN data buses. If a valid signal is recognized there the PSE control module (combined) (A37) is actuated via CAN data buses.
If the trunk lid is unlocked the LED in the remote trunk releaseswitch (N72s15) is actuated by the PSE control module (combined)(A37) via CAN data buses.
Special features on model 208.4 (Cabriolet)The trunk lid cannot be released remotely with the transmitter key.The rollover bar (RB)/soft top operation control module (N52)signals via the CAN interior data bus whether the soft top is lockedor unlocked or the power soft top switch (S84) is operated. As long as the CAN message reads:"Power soft top switch (S84) operated" or"soft top unlocked"the trunk lid cannot be released remotely.

Pneumatics testingPermissible leakage in complete system at:vacuum of 300 mbar within 1 minute: 30 mbarPermissible leakage of actuators with lines at:vacuum of 300 mbar within 1 minute: 25 mbar
Thanks

hi from uk as a getz owner(my wifes car) i do understand problem may i suggest this is most probably the lever on rear of the lockwhich is behind the cover on boothatch is probably loose hence when key is used the lever that connect to rod link and releases latch is slipping on key lock operation but when c/locking is used on drivers door it opens boot latck by motor no problem SO remove the panel from hatch held by screwsnear screen and pop plastic buttons on surround you will now have visual access to lock mech's and by using info provided above ? i am sure you can sort the problem if you use both key in lock operation and c/locking method to observe linkage it may be as suggested or a simple little ajustment of rod linkage hope this helps/inspires you ? best wishes from n/west uk lanc's

is yours the renault keycard to start and open doors?if it is a know these cards can go faulty.they were bad on renault laguna.the switch breaks off the board inside card.can be soldered back on.think you can get replacement switch kit on ebay with instructions how to fix.need someone who can solder with some eletronics knowhow.if not not sure sorry

Chances are the central locking actuator for the truck is locked up. If this is the case then you are going to have to use the key by turning it counter clockwise in the trunk lock and pushing in on the button.