Hi Steve, good question. Yes, you should be able to analyze the two languages together. Sometimes when you import a MaxDiff design, it creates a different "Design ID". So even though the design itself is identical between surveys, the software gives one design a slightly different code.
In your respondent data, find the "sys_MXDDesignID_MaxDiffExerciseName" column. This is where the software records that design ID (so it knows which items were shown in which question). There should be two values for your respondents - one for each language. If you copy the correct design ID for all your respondents, you should be able to analyze the data together.
(p.s. only copy the Design ID value if you are 100% certain the two designs are identical)