C# App has worked for years (MYOB.AccountRight.SDK.dll) Upgrade forced, now broken

Hello, 

All sorted. I should have mentioned the URI was LocalHost based so isn't a server problem, all on the same laptop. 
I fixed the issue, notes below:

5/10/23 Currently unable to use eBay tools to interact with MYOB Database since upgrade.
https://my.myob.com.au/Bd/pages/MyProducts.aspx
s/n info:
MYOB AccountRight Standard - 2023.7 - (Serial Number {removed})

Is this the connector ? Am going to try to uninstall MYOB completely and ensure following folders are empty:
C:\Users\{edit}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\ shortcuts inc MYOB AccountRight AddOnConnector
C:\Users\{edit}\AppData\Local\Programs\MYOB\AccountRight\Huxley.Application.exe
C:\Users\{edit}\AppData\Local\Programs\MYOB\AccountRight\app-2023.800.10002
C:\Users\{edit}\AppData\Local\Programs\MYOB\AccountRight\app-2023.800.10002\AddonConnector\MYOB.AccountRight.API.AddOnConnector.exe
C:\Users\{edit}\AppData\Local\Programs\MYOB\AccountRight\app-2023.800.10002\AddonConnector
Also look for adjacent folders from older installations, Search MYOB, and check registry.

Do this and then try to connect again (once successfully operating using MYOB App).
- On Add Remove there are two versions, the recently installed 'upgrade'and the original 2014.2.16.3881. Uninstalled both
- Rebooted, ran C:\Users\{edit}\MYOB Installer\MYOB_AccountRight.exe. Installed and started OK
- Opened current file > Opened OK!
- Look at connector situation > Add on connector running OK
- Try my Application > YES!!!! Everything works !!

No idea why it broke but the old Uninstall > Clean-up > Re-install worked. 

Thanks for all :D