AIOs cannot have condensation because they cannot cool below ambient.
Any liquid seen on an AIO should be handled with scrutiny as it might indicate a leak. Most of the glycol coolant many use is somewhat clear in color (or slightly yellow/yellow-green). It will likely be a bit sticky as it dries.
Hopefully you still have the purchase receipt and can RMA or return it because that will likely be your next course of action.
I've tested many AIOs and have yet to find one that had a leak when I was evaluating them, but I've seen plenty of forum postings to know that it does happen.