For everyone's awareness, the Tech Forum is not connected to the official Church support teams. The Forum primarily serves as a place for user-to-user discussion and self-help. We're (almost all) just regular members like yourself, with no special insight into anything Church IT might be doing.
It does appear that this is an ongoing issue for various members, and that standard suggestions such as using a different web browser, using private/incognito mode, or trying on a different computer, do not resolve the issue for those members. However, there are also many members who are successfully using the online Store. I'm always a fan of having lots of members submit Feedback for common issues, since there's a hope that if a lot of members all submit the same problem, it might prompt a quicker response. The Feedback tool is available at the bottom of most Church webpages (and also from inside Church apps).