Hi @minhluan259. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento give me 2.4-develop instance - upcoming 2.4.x release

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Verified the issue on Magento 2.4-develop branch and the issue is reproducible:
Steps to reproduce:

1. Create an Order from front-end
2. View Order from Front-end
3. Print Order - No issue http://magento2.4.local/default/sales/order/print/order_id/37/ - User is able to print Order and save
4. Access below Print invoice URL before the invoice is generated (using any new ID in the URL)
   /sales/order/printInvoice/invoice_id/7/

[2021-08-16 12:00:54] main.CRITICAL: The entity that was requested doesn't exist. Verify the entity and try again. {"report_id":"5aade6c95721635595e8acabec9909a13f5cf2ca4212e0313cd3e939ba435167","exception":"[object] (Magento\Framework\Exception\NoSuchEntityException(code: 0): The entity that was requested doesn't exist. Verify the entity and try again. at /var/www/html/magento2.4/magento2/app/code/Magento/Sales/Model/Order/InvoiceRepository.php:75)"} []

Note: There is no issue for the Orders having invoice generated from admin and navigated to /sales/order/printInvoice/invoice_id/7/

✅ Confirmed by @engcom-November
Thank you for verifying the issue. Based on the provided information internal tickets MC-43098 were created

Issue Available: @engcom-November, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.

@magento I am working on this

can u please check is there any third party extension you have installed that conflict with invoice process

Hi @minhluan259 ,

Thanks for your reporting and collaboration.
We have verified the issue in latest 2.4-develop instance and the issue is reproducible.
Kindly refer the screenshots.
Steps to reproduce

1. Create an Order from front-end
2. View Order from Front-end
3. Print Order - No issue User is able to print Order and save
   
4. Access below Print invoice URL before the invoice is generated (using any new ID in the URL)
   /sales/order/printInvoice/invoice_id/3/
   
5. Create the invoice and then run the above url.
   

Thanks.

Unfortunately, not enough information was provided to create a Jira ticket. Please make sure you added the following label(s): Reproduced on 2.4.x, ^Area:.*

Once all required labels are present, please add Issue: Confirmed label again.

✅ Jira issue https://jira.corp.adobe.com/browse/AC-12999 is successfully created for this GitHub issue.

✅ Confirmed by @engcom-Bravo. Thank you for verifying the issue.
Issue Available: @engcom-Bravo, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.