The link
https://en.m.wikipedia.org/wiki/2015...us_A400M_crash provides a plausible explanation of the cause and of the differing views of which agency would investigate.
The aircraft was still on test and destined as a military version, thus an ‘in house’ investigation might be appropriate (no public report), which may be a similar procedure to that under U.K. ‘B’ conditions (civil cert) [US ‘Experimental’?], but with military interest, and thence civilian EASA interest because of the dual certification, and some local infighting, no clear EASA policy, etc, etc...
The software explanation is also plausible (Ref 32, 33); preflight test calibrations / checks could reset systems or dump critical data so that the FADEC could not control the engine (other than on the ground / takeoff power), and being ‘Full Authority’ this might result in a frozen engine or auto shutdown in the air. The latter appears most likely.
Has the type actually achieved civilian certification, or a civilian aircraft formally registered ?