I suspect that you have 4 Ethernet connected PC’s either connected directly yo the BT router or a switch which also has a Ethernet connection to the router.

One of your replies makes me suspect that the pc’s are dropping the Ethernet connection due to non use over a period or […]

Resolution for 'BT router issue: 'QuickBooks Aborts in Multi User Mode' available: Yes.

The BT router 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 BT router issue yourself by looking for a resolution described in the article. If it is a complex BT router issue or you are unable to solve the issue, you may contact us by clicking here or by using other BT router support options.

For more information about resolving issues related to BT router in Quickbooks/QBO or to get support for the issue 'QuickBooks Aborts in Multi User Mode', click the link below: