Try this article:

https://community.intuit.com/articles/1502420-error-6123-0-when-updating-or-opening-company-file

Resolution for 'code 6123 issue: 'what do i do if i get error code 6123,0?' available: Yes.

The code 6123 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 code 6123 issue yourself by looking for a resolution described in the article. If it is a complex code 6123 issue or you are unable to solve the issue, you may contact us by clicking here or by using other code 6123 support options.

For more information about resolving issues related to code 6123 in Quickbooks/QBO or to get support for the issue 'what do i do if i get error code 6123,0?', click the link below: