Let me help you with this.

Since you’ve already uninstalled and reinstalled the app, let’s try resetting the application.

Here’s what you’ll need to do:

  1. Right click the Application icon and quit.
  2. Launch the application while holding the Function (fn) key. A prompt to reset the app will appear.
  3. Follow the instructions […]

Resolution for 'already uninstalled issue: 'QB Online for Mac App Login Problem' available: Yes.

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

For more information about resolving issues related to already uninstalled in Quickbooks/QBO or to get support for the issue 'QB Online for Mac App Login Problem', click the link below: