You have to disable sleep on the host computer.  Apple Menu->System Preferences and then click on Energy Saver.

Resolution for '2016 Server issue: 'Quickbooks Mac 2016 Server Disconnecting When MBP Goes to Sleep' available: Yes.

The 2016 Server issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the 2016 Server issue yourself by looking for a resolution described in the article. If it is a complex 2016 Server issue or you are unable to solve the issue, you may contact us by clicking here or by using other 2016 Server support options.

For more information about resolving issues related to 2016 Server in Quickbooks/QBO or to get support for the issue 'Quickbooks Mac 2016 Server Disconnecting When MBP Goes to Sleep', click the link below: