QuickBooks Desktop

I've checked here on my end and found no related issue about the error message you've encountered, @soztalay.

Let's work together and get around this error. You'll want to ensure you have a stable internet connection to isolate and fix this issue. 

If this is not the case, I suggest updating your QuickBooks Desktop (QBDT) to the latest release to ensure you have the newest features and fixes. I'll show you how.
 

1. Go to the Help menu and select Update QuickBooks Desktop.
2. Select the Update Now tab. You can also select the Reset Update checkbox to clear all previous update downloads.
3. Click Get Updates to start the download.
4. When the download finishes, restart QuickBooks, and accept the option to install the new release.

You can also see this link for more details: Update QuickBooks Desktop to the latest release.

Also, QuickBooks release an update about service discontinuation to older versions of QBDT (2019 and older). Rest assured you can still use your old version of QBDT. To enjoy the full service that QuickBooks offers, you'll want to upgrade to a newer version of it.

I'm also attaching this resource that will help you learn some best practices for managing your multi-user network: Set up and install a multi-user network for QuickBooks Desktop.

I'll be around if you have any other concerns or questions about the multi-user mode. Just add them in your reply and I'll take care of them for you. Take care!

I was hopeful that the "Reset Update" was going to work but that didn't work either.

I have been using One-Drive to store my file but this has never been an issue... I have also worked off a thumb-drive in the past which also wasn't an issue.  So the location of the file has never been an issue regardless if it's a local PC, thumb-drive or One-Drive.

It appears everyone that I've talked to at Intuit/QuickBooks is saying the same thing.... "upgrade to the latest version".  Honestly, QuickBooks 2018 Pro does everything I need... this annoying pop-up just started for no reason.  My thought is that you guys have time-bombed older version to get everybody to migrate to a subscription program.

@soztalay 

Are you still able to open your QBD file(s) locally on your machine? If the answer is yes, it's most likely an update in OneDrive and it's no longer working with QBD 2018. You can still purchase the one time license for QBD 2021 to upgrade your version if required.

I put the file on a thumb-drive too and had the same error message.... not sure that One-Drive is the problem...

I copied the file to a thumb-drive and had the same issue... not sure One-Drive is the problem.  It is interesting that when QuickBooks is left idle nothing happens but when I click on something then the error message appears...  Based on conversations that I have with Intuit/QuickBooks employees, it appears everyone keeps bringing up "upgrade"... I have no reason to upgrade because I don't need the new features... what I have works perfectly (even with the annoying error message and restarts)...  I get the feeling the app is "time-bombed" that after a certain date or app starts that this error message appears (kinda like a virus) and the solution is upgrade to the new subscription version....  one can only wonder..

If you are not able to restore it from your thumbdrive, your file is damaged. Run QB ToolHub to fix it. Otherwise, consider purchasing a 3rd party file repair service.