QB Issue Resolution:

Sorry – we had an issue with the signing of the R2 update earlier today. The R2 update disk image has been just been updated this afternoon and is available from the Product Updates site …
If you encountered a problem launching QuickBooks 2015 R2 on your Mac from a previously acquired disk image, please go download (re-download) the R2 update and re-install your QuickBooks app.

Resolution for Issue 'Quickbooks 2015 is damaged and I should put it in the trash' available: Yes (Solved).
Source: Intuit Community forum.

Quickbooks 2015 is damaged and I should put it in the trash: this 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 issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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