I'll make sure that your customers can view the invoices, rpropertyservi.
Most of the time, viewing issues are cause by the accumulated cache in the browser. To rule this out, you can let your customers open the invoice in a private or incognito window. This mode doesn’t store any cache, cookies, or site data. Here are the shortcut keys:
Ctrl + Shift + N for Google Chrome
Ctrl + Shift + P for Firefox & Microsoft Edge
Command + Shift + N for Safari
If they're able to view the invoice with out any issues, they'll have to go back to their regular browser and then clear its cache to delete the stored temporary internet files. They may also use other supported browsers as an alternative.
In addition, you'll want to make sure that your customers are using the latest version of Adobe Reader/Acrobat. QuickBooks Online uses this application to control and manipulate the sales forms.