Why has Gibraltar still not reached a Brexit deal with Spain?

With yet another round of Spain-UK negotiations set to begin more than eight years since the Brexit referendum, Gibraltar is still without a deal and a November deadline looms over any treaty. Why has it proven so hard to break the deadlock?

Why has Gibraltar still not reached a Brexit deal with Spain?
With yet another round of Spain-UK negotiations set to begin more than eight years since the Brexit referendum, Gibraltar is still without a deal and a November deadline looms over any treaty. Why has it proven so hard to break the deadlock?