An xcd file is the settings file resulting from the use of MultiTerm Convert. This is not a MultiTerm Termbase.
If you have not actually converted anything then maybe try again using SDL MultiTerm Desktop. If you deliberately used MultiTerm Convert then you need to take the files and use these to create your Termbase in MultiTerm Desktop.
Sorry if I have misunderstood you, but perhaps the video here will help you, prepared by Nora Diaz and very easy to follow:
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