Access Denied message on client end invoice viewing.

Self-Hosted | v4/Legacy
1

When my clients try to view an invoice. They are getting an access denied message.
They can click OK to this message and the invoice will display correctly and everything works as expected.
Has anyone else had this issue?

2

It may be related to their PDF reader

https://kb.globalscape.com/KnowledgebaseArticle11046.aspx