As of September 20, 2018, Intuit deprecated TLS 1.0 and 1.1 to improve security protocols. All QuickBooks Online users need to upgrade their applications to TLS 1.2.
This update affects the FM Books Connector Online plug-in. As of version 2.0.4.0, we have updated the plug-in to explicitly use TLS 1.2+ security for authentication and data transmission to QuickBooks Online.
As long as a client is using v 2.0.4.0 or above, which was released on July 2, 2018, they are compatible with TLS 1.2 and will be able to continue to use the plug-in. Any version of the FM Books Connect Online plug-in prior to v 2.0.4.0 will not function after September 20, 2018, due to the Intuit changes.
A client’s FM Books Connector Online subscription includes free upgrades of the plug-in.
Additional information on TLS 1.2 can be found here: https://developer.intuit.com/hub/blog/2017/08/03/upgrading-your-apps-to-support-tls-1-2.