It's narrowed down at this point. If the two midbass drivers are functional then the input to the passive criossover is fine up to that point. If the tweeter diaphram was changed out but the tweeter still does not operate then the issue would appear to be within the speaker's passive crossover board. It could be a series capacitor within the passive highpass filter or a cold solder joint at one of the board components or tweeter output terminals. The tweeter crossover frequency and slope would be changed if a parallel crossover component was out or disconnected, but the tweeter would still play. So again, knowing how all the elements work, you have already narrowed the issue down considerably to just a couple of possible culprits.
If you could identify the filter schematic on the crossover board then it is very simple to jumper around various series highpass crossover components and contact points with a fullrange speaker in order to isolate the issue. That is a lot to ask someone to do in the field. However, this is exactly the next step that your dealer or manufacturer would take if the product was in their possesion.
A field repair by the consumer is rare. Normally you would immediately return the product to your dealer so that they could do all this for you. But if you are in a rush and do not have time for the round trip then you can change out the passive crossover board in the field. It's a job to replace the tweeter diaphram. Changing out the crossover board really isn't any more difficult. Just label the input/output leads and corresponding terminals before removal.
Either Odin at Earmark or the Wetsounds staff can walk you through exactly what to do if you do not want to ship the speaker.
Both are in Texas so they have an early start on you tomorrow morning.