I had a similar issue, where I purchased a chest with (before I knew about the update), but it would not open. Aarik resolved it.
Today, I read in the update notes that the first time you complete a scenario you gain a treasure chest so I decided to delete my other parties and run with all new Characters (classes I have never played in real life, too). After the scenario the chest appeared, but I couldn't open it!
My PFID # 12B 82FB 474 169 B86.
I can send a screenshot showing the chest glowing gold and sparkling, but it will be the same as the one I sent a few days back. If it's preferable that I send a one-on-one email, let me know. Thanks for helping me previously, too!