Several times today, when I've been buying from a non-main shop (ie. Quest Shop, Medicontra), I've gotten the following message:

[box=#ffaea8]Oh No! Looks like the page refreshed. You are seeing this message to prevent you from accidentally making a duplicate purchase.[/box]

However, I've not refreshed the page and the purchase seems to go through.

Chrome 78.0.3904.108 / Mac OS X

From what I've heard, I think it's been doing that when the site has been laggy, sometimes your browser might try to send the request through more than once if the page isn't responding right away, so even though you're not actually refreshing the page, it's still registering as a duplicate attempt to purchase the item, so that message pops up instead to prevent it from going through again.

Ah, okay. That makes sense.

It's just annoying because I'm trying to unlock some of the challengers that want you to buy items, and it seems to be preventing that (and/or I'm just having trouble following the directions off the battle thread page, haha.) I can just try that again later; perhaps the lag is also slowing the notifications from popping up.

Well the purchases should still go through (at least they have been for me), it's just to prevent you from accidentally buying something like 2 or 3 times if you didn't want to do that. So it's not really an error as in, you can't purchase anything. It's just there to protect you from buying more than you may have meant to.

[edit]Although if you're trying to unlock battle challengers, some of them have been having issues unlocking lately. Which ones specifically are you trying?

Quentin and The Healer -- but I just got the healer when I visited her for battling, so it finally came through? I'm not too worried about it though. Thanks though!

--

So probably just the site being laggy, this is probably resolved.

No problem!

For Quentin, you could check the secret tab and see if they unlocked anyway. Sometimes it might go through even if you miss the event that tells you.