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Welcome to the forums!
It's not actually undergoing maintenance. I have seen several threads in the forums where people reported problems; you may try looking for solutions in other threads. I would simply suggest to update the store app if you haven't recently, and perhaps it would help to delete and redownload it.
Also, this topic would fit best in the Playstation Network Support forum (link below), which is where you could search for related threads. It isn't an issue with the forums, which is what this section is for.