There can be a variety of reasons why visitors are not subscribing to your notifications.
Having a poorly designed store makes a bad first impression. Make sure your store visitors have a great experience browsing your store and have a simple checkout process without too many pop-ups and obstructions.
Maybe your store is selling products which have a long life cycle (example - laptops, accessories, etc.). Such products typically don't need regular updates once purchased. So visitors might not feel the need to subscribe for notifications.
Are you running Facebook or Google Ads for your store? While you might be getting a lot of traffic from these ads, if they're not focused on your target audience, the visitors from these ads might not be interested enough in your store to subscribe for updates. Consider assessing your ads targeting if you're facing this issue.
Offering an incentive like a small discount coupon works wonders in converting visitors into subscribers. Edit your PushOwl widget message to include the discount code or offer.