Thanks for checking in with us, AlexGold.
I'm here to help you with migrating your 2016 file to 2019. Let's get this sorted out.
To better isolate the issue, you may want to update your QuickBooks password. Complex passwords must be changed every 90 days. QuickBooks prompts you to change your password near the end of the 90 days as well as on the expiration date itself.
After updating the password, you can follow the steps below to migrate your file to 2019.
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If you'd like to go through this over the phone, you can call our dedicated team who will be happy to assist you. Our contact details can be found here along with our opening hours.
Let me know how it goes by leaving a reply below or if you ran into a different situation so I can look further into this.
QuickBooks Mac doesn't require the files be upgraded every 90 days. But you will have to update the passwords when upgrading to 2019 for the first time. User passwords have t one reset - there's no way around that as its technically necessary.
2019 has now been out since last September - you shouldn't encounter any corruption issues. But then there shouldn't have been corruption issues before, either. Given the large number of company files my concern is that you may have the company files on a network drive that is sharing them. That isn't supported and it is possible to experience corruption of CoreData files when operating with network file systems (this has been documented by Apple in their CoreData notes).
Instead, if the files are shared over a network, the supported way to accomplish this is via the QuickBooks Server application. With 2019 it may also be possible to share the files via iCloud or another file sharing service. In that case the users would open the local copy of the file created by the sharing service (DropBox, GoogleDrive, etc). The only officially supported one is iCloud but the others should also work - its best to conduct a test first.