I downgraded/reinstalled Microsoft Office and XL-Connector stopped working

This issue may occur for users running a 32-bit Office on a 64-bit Windows machine. The best way to resolve it is to install a 64-bit Office, but it may be possible to fix it by making some changes to your registry:

1. Go to the Settings dialog of Enabler and copy the link to your log file.

2. Open Windows Explorer and paste the copied link into the address bar. The log file will open in your default text editor.

3 Look for error messages closer to the end of the log file. The right message will contain something like “Unable to cast COM object of type ‘System.__ComObject’ to interface type …” and also “call on the COM component for the interface with IID ‘{000C03A7-0000-0000-C000-000000000046}’ failed due to the following error: …”.

4. Copy the long IID string (without braces).

5. Click Start and type ‘regedit’, then hit Enter

6. In the Registry Editor that opens find the following key:

32-bit systems:
 HKEY_CLASSES_ROOT\Interface\{IID-THAT-YOU-COPIED} 
64-bit systems:
 HKEY_CLASSES_ROOT\Interface\Wow6432Node\{IID-THAT-YOU-COPIED}

With the subkeys:

 - ProxyStubClsid - ProxyStubClsid32 - TypeLib

7. Take a look at the (Default) and Version values inside of TypeLib.

8. Now find the node below, using the (Default) value as <TypeLib ID>.

 HKEY_CLASSES_ROOT\TypeLib\ <TypeLib ID> \

9. As child of this element you will find more than one element, one of them is the Version from the first registry entry (under HKEY_CLASSES_ROOT\Interface). If you inspect the others elements, you will find that they point to nothing.

10. Remove all these elements except for the version identified in point 9.

11. Restart Excel and it should start working correctly

The solution has been taken from StackOverflow