If you accidentally installed the 9.71 or 9.72 API in your system, you’ll find out that it breaks BT. And you can’t go back to the 9.70 API no matter how many times you uninstall and reinstall the API’s.
Here are the steps to COMPLETELY uninstall the current API so you will be able to reinstall the API version which BT uses.
1. uninstall the “TWS API” program from the Control Panel.
2. manually delete the “C:\TWS API\” folder if it is still there
3. manually delete the C:\Windows\SysWOW64\TwsClientSocket.dll” file
4. reinstall the version of API you want.