In SDL MultiTerm Extract you set the Export Settings in the Export Wizard. When trying to create/select a termbase definition from an existing SDL MultiTerm termbase created in SDL MultiTerm 2014 or 2015 the following error is displayed:

Error retrieving termbase definition.

Workaround 1:

Create the termbase you want to use in SDL MultiTerm Extract through SDL MultiTerm Desktop 2011.

Workaround 2:

1. Open  MultiTerm and the termbase you created for the SDL MultiTerm Extract project.
   Note: Ensure the user interface language in SDL MultiTerm Desktop is set to English. If this is not the case go to View > User Interface Language and change it to English (United States). If this is not applied the following steps will not work.
    
2. Click Termbase Management and save the Termbase Definition in a location of your choice.
3. Close SDL MultiTerm Desktop and go into the folder where the Termbase Definition is located.
4. Open the file with the *.xdt file extension in a Text Editor e.g. Notepad or Notepad++
5. Do a search and replace:
   
   Search string:
   
   <TextChild xmlns:dt="urn:schemas-microsoft-com:datatypes" dt:dt="string">Language level</TextChild> OR <TextChild dt:dt="string" xmlns:dt="urn:schemas-microsoft-com:datatypes">Language level</TextChild> 
   
   Replace string:
   
   <TextChild xmlns:dt="urn:schemas-microsoft-com:datatypes" dt:dt="string">Index level</TextChild> OR <TextChild dt:dt="string" xmlns:dt="urn:schemas-microsoft-com:datatypes">Index level</TextChild>
6. Save the changes and close the Text Editor.
7. Open SDL MultiTerm 2014/2015 again and create a new termbase based on the Termbase Definition that was modified.
   Note: More information about creating a termbase based on a termbase definition can be found here
   • How to create a termbase from a termbase definition (XDT) and termbase data (XML) file in SDL MultiTerm
8. This new create termbase can be used for the SDL MultiTerm Extract project.

As of SDL MultiTerm 2014 (and later) the term Index Level was replaced by Language Level in the user interface (UI) and this also had to be done in the "background" where data is saved/created like in this case for the Termbase Definition. SDL MultiTerm Extract cannot handle that difference yet when trying to retrieve information from the Termbase Definition of the termbases created in SDL MultiTerm 2014 (and later) and therefore you see this error message described in the Symptoms section.

The SDL Development team is aware of this problem and is working on a solution. Until a permanent solution is in place, you can apply one of the workarounds described in the Resolution section.