Hello,
I have checked your shop page now, and it is working fine.
See Screenshot for clarification: https://postimg.cc/Bjw3bdfc
Usually, if re-saving permalinks temporarily fixes the issue, it may be related to permalink/cache conflicts, server cache, security/performance plugins or a plugin conflict affecting rewrite rules.
Please try clearing all cache (plugin/server/CDN), temporarily disabling optimization/security plugins, and checking if the issue appears again.
Best Regards