This is Rae from Shopify. Thank you for reaching out about printing order sheets in bulk, and welcome to the Shopify Community. I'm glad to lend a hand with this query.
I'd really like to hear more about the troubles you're encountering when using Order Printer on your Mac so that we can resolve these issues and get the app working on your account. With this in mind, can you please confirm what problems you had with the app, or if any error messages appeared while you were using the app? If so, feel free to send me a screenshot showing these errors so that I can take a closer look into this.
You also mentioned that you cleared the cookies and cache on your computer already, which is a great step. Which browser were you using when you completed this? Have you tried using Order Printer from another browser - like Chrome, Safari, or Firefox - to see if the app works correctly in these browsers instead?
In the meantime though, I wanted to touch on your comment about bulk printing with Order Printer. It's important to confirm that Order Printer can only print up to 50 orders at a time using bulk actions. With that said, to print 300 orders using Order Printer, it's best to print the orders in batches of 50 orders at a time.
If you prefer to use another app to print these details instead, some options I recommend looking over to print invoices and packing slips in bulk are Ordersify or Order Printer Pro, which both offer free plans for up to a certain amount of orders. These are both third-party apps, so to learn more about their features and costing, I recommend reaching out to the app developers directly for more information. You can contact them by following these steps.
Please keep me posted on the above! I look forward to hearing back from you with more details.