There can be a variety of reasons why subscribers are not interacting with your notifications.
The primary factor might be that the copy of your notifications is not catchy or interesting enough to engage your subscribers. You might be selling the best product amongst all your competitors, but if your message if dull, it does very little to excite your subscribers. Make sure your notifications are interesting and it'll work wonders for your store.
Another reason might be that your notifications might not have a good incentive for your subscribers to click on them. You could try providing them a small discount or offer which will interest them to click on your notification.
Also, consider whether your subscriber base consists of your target audience. If your subscribers are not your target market, then they won't be interested enough to click on your notifications.
Try working on these aspects if you identify with any of them.
Don't give up. Your breakthrough might be just one attempt away.