The reason you're seeing a 'blank' for the %device% is that %device% is populated by the device that triggered the rule. Since you're using a Specific Time as a trigger, %device% will not be populated.
Instead, you would want to have a simple IF statement for each door as follows:
IF (Door 1 open(F) [FALSE]) Notify Mobile (hubitat): 'Door1 is open!'
IF (Door 2 open(F) [FALSE]) Notify Mobile (hubitat): 'Door2 is open!'
IF (Door 3 open(F) [FALSE]) Notify Mobile (hubitat): 'Door3 is open!'
IF (Door 4 open(F) [FALSE]) Notify Mobile (hubitat): 'Door4 is open!'
I'm just really glad you weren't trying to get a TTS announcement. I saw the title and I thought, oh no...not again. Trying to get it worked out so that the list can be spoken and also sound human is a real PITA. The complexity of getting a phrase like "The garage and side doors and bedroom and living room windows are open." from just a list of devices is no small feat. Working through that you really get a feel for how complicated voice assistant systems really are.
That said, if you do want to ask Google what the status of your devices are, the new Google Home community integration supports all the device types that Google does. So you can sync doors/windows to Google and ask Google if a window is open or closed or is a door is open or closed. Therefore letting Google do the heavy lifting of coming up with the appropriate response.