A couple of things are possibly going on.
GOG Support may be overwhelmed with the summer sale and the influx of new customers, and are prioritising transaction issues related to the sale.
It's also possible that your ticket has fallen through the cracks (again, perhaps due to the summer sale and an increased number of submitted tickets).
Since you got the automated email, reply to that; it may get the attention of a GOG staffer.
Whatever the case, I can understand your frustration, especially if your problems can't be solved and you get a refund/store credit when the sale will be already be over.
JMich: Be aware that support is also working on weekends. It's no longer a week day only job, but 4 week days and 1 weekend day job. At least that were the requirements in a customer support position GOG had posted a while back.
While true, does that requirement actually mean that the whole GOG Support crew is working during weekends? My guess is no, just that GOG has a cut-down support team working during weekends - how cut down, is anyone's guess. That would indicate that they're doing some prioritising during the weekends as to which tickets to address, especially when a big sale like the summer one is live.