Link to customer invoice

Hi,

No.
However, I believe the solution is elsewhere.
If you have enabled the order statuses for which you want the customers to be able to get their invoice in the column "print invoice" of the menu System>Order statuses, then they will be able to get the invoice themselves on the order details page of their order on the frontend.
Also, you can use the PDF invoice plugin to have a PDF of the invoice included in the email notifications sent to them:
www.hikashop.com/marketplace/product/18-plugin-pdf.html

Hi,

The order details page is available even to guest users. So it's not a problem.
In the email notification that your guest customers receive there is a link to their order details page. That link contains a token specific to their order so that only them, with the correct token can access the details of their order.

Hi,

This means that the menu item with the id 1024 is not set to "public" access.
What is that menu item ?
And which payment method are you using ?
Normally, the confirmed email notification is generated after the order status is changed to confirmed, when the payment gateway sends a payment notification request to the website. And normally, the URL of that payment notification includes that same Itemid parameter which is then used to generate the link in the email.
And normally again, the payment plugin sends to the payment gateway that payment notification URL at the end of the checkout using the menu item on the checkout.
So if your checkout is accessible without a user account, then the link in the email should be accessible without a user account.
So before I could give a solution, I would first to better understand how your checkout and payment method is configured and what menu item is used on the checkout. If you're using a third party payment method, it's possible that the payment plugin doesn't set the Itemid properly in the payment notification URL. So it you would actually have to check with the developer of the payment plugin what's up with the Itemid for the payment notification URL.

Hi,

Turn on the "error reporting" and "debug mode" settings of the Joomla configuration and try accessing that page.
You should then get more information on that error and that will allow us to tell you what to do.

Hi,

The error comes from the "tagz" plugin of the group "system" that you have installed on your website.
It seems it has trouble loading the tag parameters.
If you disable that plugin, you should not have that error message.
I would recommend to report that issue with the full error message to the developer of that plugin so that they can check what to do and probably update the plugin to avoid that error.