When you unlock car doors unlock but boot doesnt?

The trunk/boot unlock is always a separate button on the key fab. Unlock usually only unlocks the driver's door when pressed once and all doors when pressed 2 times.

But if you are following the correct procedure to open the trunk/boot via your vehicle's remote, a failure of the trunk/boot opening mechanism is also a possibility. They typically have a plastic tab which can break off, disabling the trunk/boot from opening. This would have to be replaced if that were the case. A failure in the electrical circuit is another possibility.