我昨天遇到，steam support回复：
Are you attempting to make the purchase through Steam or with a web browser using the storefront webpage?
If using Steam, try the following:
If using a PC
-Exit Steam, then go to the location that Steam is installed to. By default this is C:\\Program Files\\Steam directory (this is the default with a Steam installation - if you set a different installation directory, you will need to browse to it).
-Delete all of the files except for:
Steam.exe
And the folder \\SteamApps\\
If using a Mac:
-Exit Steam and go to the folder Users/[username]/Library/Application Support/Steam
-Delete all of the files in this folder except for SteamApps.
Restart your computer and test the issue.
Note: This process will not affect your currently installed games.
If the issue still persists, try using a web browser (Internet Explorer 7 or higher, or Safari or Firefox if on a Mac) to make the purchase using http://store.steampowered.com/
If it still fails, try logging into your Steam account and making the purchase directly through the Store interface.
直接这样贴没违反版规吧？
※ 引述《taiwan540 (死阿宅)》之铭言：
: 不知道有没有人跟我遇到一样的问题~"~?
: 原本买的好好的
: 帮我自己跟朋友总共买了四个Payday2跟两个DLC后
: 想再补买两个DLC
: 从下午五六点就开始一直收到同样的讯息了...
: "发生意外错误。购买未完成。请连络 Steam 客服。"
: 什么东西都买不了
: 网络上的各种解决方法几乎都试过了
: 请问还有解吗?
: 难道只能眼看着Payday2的优惠时间过吗...!?

谢谢分享 但我刚刚都试过了T_T 无解啊~~

那只能找朋友帮，我等steam回信就是找同学用送礼的

这些是罐头回复 叫你重装Steam而已