A recent update to Microsoft Office broke the Word templates produced from Dynamics GP for both workflow notification/action emails and emailing of Word template documents (such as remittances, orders, invoices and so on). A few days after Microsoft shared details of the problem, they said a fix would be forthcoming and it is included in the 2020 Release.
This does mean that if you are on any version of Dynamics GP 2018 or on the 2019 Release, you will need to apply the 2020 Release update; a fix for Dynamics GP 2016 will also be released, but the method of approach is still being determined.