There is a bug in El Capitan, restore your old OS, print to .pdf and attach from Mail, stand by until Apple/Intuit releases an update.

Resolution for 'Appleupdate issue: 'Why is Quickbooks Mac not attaching estimates and invoices in emails to customers. This problem began when I download the new OS El Capitan.' available: Yes.

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

For more information about resolving issues related to Appleupdate in Quickbooks/QBO or to get support for the issue 'Why is Quickbooks Mac not attaching estimates and invoices in emails to customers. This problem began when I download the new OS El Capitan.', click the link below: