Yes.  I have a client with SAUS 2012 that does not work once the Jan 2019.1 got installed.  Sage Tech support suggested that it's possible the .Net 3.5 framework was corrupted but my client's tech support didn't explore that possibility and left them on a single-user only virtual machine to run the company.  They have 4 machines that need to use that company file.

I think when I tested my notebook (Win8.1), SA 2012 didn't work either.  I don't have SA2009-2012 on my desktop and never reinstalled my US versions either.  However, 2008 and 2013 and higher work ok on my desktop (Win7).

A bookkeeper/partner in BC had problems with his 2013 after 2019.1 was installed so he dropped back to 2018 and didn't bother to upgrade because he needs 2013 for his own company.

If you find a solution, let me know.

Yes.  I have a client with SAUS 2012 that does not work once the Jan 2019.1 got installed.  Sage Tech support suggested that it's possible the .Net 3.5 framework was corrupted but my client's tech support didn't explore that possibility and left them on a single-user only virtual machine to run the company.  They have 4 machines that need to use that company file.

I think when I tested my notebook (Win8.1), SA 2012 didn't work either.  I don't have SA2009-2012 on my desktop and never reinstalled my US versions either.  However, 2008 and 2013 and higher work ok on my desktop (Win7).

A bookkeeper/partner in BC had problems with his 2013 after 2019.1 was installed so he dropped back to 2018 and didn't bother to upgrade because he needs 2013 for his own company.

If you find a solution, let me know.

Then have another client that needs to run 2011 and 2019.2 so they installed .2 CM only on server and their 2012 no could no longer access 2011 data on server. So had to upgrade 2011 to 2013 (luckily they had an old licence). Even then they were having issues so I had to install 2019.2 on the "2013 only workstation" so the data could access the data. Bottom line is the compatability of all Sage versions harmoniously is gone. We will have to start dedicating machines to run specific version of Sage. .Net mumbo jumbo 

It was a nice run and it made a lot possible complicated issues for us a lot easier.  There is no way I'm going to be dedicating machines, I don't have that kind of budget.  Tony did that for repairs and even he had trouble keeping track of them.

I spoke with HA directly and got a lot of good info from him.  He tried to help and even ran some tests on their systems for comparison but didn't have any problems and couldn't replicate it.  I even installed the latest 2019.3 on that system with the US 2012 problems last week and the IT guy wouldn't answer my question about whether they checked the .Net 3.5 framework corruption possibility.  I haven't tried to play with mine to see if it will fix it but that idea came from HA.  I've never seen any other program corrupt the .Net framework though.

If you have a couple of minutes, I am about to post an response to the Transaction is not balanced thread in AP/AR forum.  Can you have a look and see if you see anything I'm missing?

It looks as if the answer is buried in this technote 
https://docs.microsoft.com/en-us/dotnet/framework/deployment/side-by-side-execution
As for the IMP purchase order you would have to send me the import file.

I've just uploaded the file in the thread:

https://www.sagecity.com/ca/sage_50_accounting_ca/f/sage-50-ca-partner-general-discussion/130612/any-other-partners-having-problems-running-2012-and-2011-after-2019-2-upgrade/349329#349329

Thank you for your assistance!