QB Issue Resolution:
Actually, we realized that the 2016 Quickbooks file was in Windows format and therefore, it needed to be converted to a Mac format (qqb).
Once we did this, we managed to open the Company File from Quickbooks 2019 without difficulty and what is more, Quickbooks no longer asked us to input a password.
It should be noted that Quickbooks 2019 did not automatically ask us to update/upload our company file from the previous Quickbooks 2016 version. In our view, it should have been the case in order to ensure a smooth transition between the two versions.
Resolution for Issue 'Why Quickbooks 2019 for Mac is asking me for a password to open my company file from Quickbooks 2016 for Mac ?' available: Yes (Solved).
Source: Intuit Community forum.
Why Quickbooks 2019 for Mac is asking me for a password to open my company file from Quickbooks 2016 for Mac ?: 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.Support for quickbooks 2016
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!
Error Recovery for quickbooks 2016 [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.
Additional Support Options: