The language pairs are the same, but in Spanish you have different options, perhaps the TM has Spanish from Spain and the document has Spanish from Puerto Rico, for example.
To solve this problem:
1. Please
EXPORT the TM, so that you get a .txt TM,
2. Then
CREATE a new TM with the language pair of the document (be careful with the different options of English and Spanish)
3. Finally
IMPORT the .txt TM...
et voilà!
