I am unable to email invoices to our clients. I get this message
Value cannot be null. (Parameter ‘address’)
Sounds like 1) your customer does not have an email address entered or 2) your email is not setup correctly or 3) you are using an outdated version of Manager
The current version of Manager does not officially supoort sending pdfs to customers - it still does but it is not supported.
The recommended way to do this is to use the Print to Pdf function of your operating system and your email client external to Manager
It should still work but you need to follow the steps here Email transactions and reports | Manager and post the screen shots