POS Sales Invoice Issue (Error in Log)


Hi @rohit_w,

The Env: Ubuntu hosted ERPNext 10.0.19 accessed from Windows 7 client PC via wireless LAN setup

There’s an error showing up in the web.error.log file many times daily as detailed below:

Error handling request /api/method/frappe.async.can_subscribe_doc:sid=xxxxxxxx

TypeError: argument of type ‘NoneType’ is not iterable

doctype = Sales Invoice
document = New Sales Invoice 1

Some consequence seems to be that it forces worker to exit, shuts down master and starting gunicorn

BTW, am still trying to figure out why the POS Sales are at times submitted and printed in duplicate or triplicate with single click of the Submit+Print buttons

What could be causing this issue? Any help is as always highly appreciated.

Kind Regards,


I have tried to replicate the issue on local account but not able to replicate it. Are you using online POS or offline POS?

Can you share the complete traceback of an error

I am using online POS.

Sorry I am not n the retail store at the moment but that is the gist of the error I scanned the log file and did not see much else but will check again and share when I have access to it.

Should I maybe switch to a wired LAN setup if signal timeouts are an issue because Server connectivity is also an issue at times i.e. screens seems to hang ?

Just wondering…