Hopefully I can help.
Here are the steps I use:
First, prior to launching the sim, use the 737 Max configuration tool to check/set a fuel level that is lower than your trip fuel for your next fight. Typically I have around 2-2.5 tons of fuel left in the wing tanks.
Then, via GSX call the fuelling truck.Wait until it arrives. One fuel truck from GSX should appear under the wing.
GSX should prompt you to wait until the fuel truck is ready to start it process.
At this point, go into the fuelling option in the Max EFB, set the new quantities for the fuel in the wing tanks and center tank (if needed) for your flight and then click on the fuel valves to open them. Click Set. You will notice externally that this action has called a 2nd fuel truck, this time from the Max itself.
GSX should start the fuelling process animation and the progressive fuelling should also start in the MAX (increasing qty in the tanks displayed in the VC) , hence both procedures are aligned/"synced".
Wait until the fuelling is complete. The GSX fuel truck will depart. This will leave a remaining fuel truck that is called by the Max refuelling process. You can request this truck to leave again in the EFB Sim options in Ground Support option where you can tell the fuel truck to disappear.
Fuelling process is now complete.Continue with remaining flight prep steps.
Note: I haven't explored if the Max fuel truck can be made to disappear when initiating the fuel upload. I suspect if you tell it to leave the fueling will stop. It may be possible in some config options but have not looked closely. This is the only anomaly I have found but the fuel process itself works consistently well.
If you have issues, report back here and I can try and help.
Regards
