Can you provide a schematic of your system or some pictures?
If you truly aren't getting any voltage at the mc4 connectors then it has to be the panel, the junction box on the back of the panel, or the wire/connector. If you have multiple panels and zero voltage then it becomes pretty unlikely that it is multiple failures coincidentally.
Can you give use the model number on the panels? Was there any shading of the panels? Was the dirt enough to shade a portion of the panel? Are the panels all wired in parallel or series/parallel?
