Sony A7M2 (ILCE7M2) update fireware to version 2.0 with uncompressed raw, but my Lightroom 5.7.1 can't support this format.
Do I have to upgrade to Lightroom 6? (It's so...)
Is there any plan to support it at version 5?
Are you certain you have Lightroom 5.7.1 installed? According to the following link, the camera should be supported in that version:
Or, is it possible that you have a different camera model number?
I believe you need LR v6.2 as for the R2 ... Sony a7r II uncompressed raw file support in Camera Raw and Lightroom
The uncompressed RAW support only appeared in November 2015.
I would try a trial of v6.2 or you could download the current version of the DNG converter, convert to DNG and then import into v5.7.1
Adobe will not update older versions of Lightroom, only the current.