2009 Volvo XC70 Tailgate Open warning

I have a 2009 Volvo XC70 that is showing me the Tailgate Open Warning in the warning section of the cluster. At the same time the tail gate close button stopped working, the tailgate wiper stopped working and the tailgate defroster stopped working. Seems like quite a coincidence that all thes things stopped working at the same time when the day before everything was working fine. I have tested the relays in the cargo compartment and there is continuity in all 3 relays. When I turn on the rear wiper switch I hear the relay clicking as well as the rear defroster too. All fuses are good and wiring still looks new. Has anyone experienced this issue and found a solution?

I haven't had that exact problem. But, the fault to concentrate on is the door-open sensor. Why?...because the other glitches are related to it either in software (the other functions are inhibited when the software thinks the door is open), or in the hardware:
-- wiring (one or multiple wires are compromised, including the one reporting of the door-closed/door-open state). OR
-- door-open sensor is failing

Where to start: I would inspect the hinge flex-harness (open one end of the rubber boot), are any wires showing bare copper?

If that looks OK, I'd next remove the tailgate inner panel to expose the door closure mechanism. If you can locate the door closure sensor wires, short the signal side to ground (power on), and see if the dash display shows door closed -- if so, the sensor is your problem -- either adjust the sensor mechanically to get it triggering, or replace it.

Thanks, I'll give that try and see what happens.
Thanks!

This video might help:

https://www.youtube.com/watch?v=PRIUBEqEgAA