The Fritz!Box 7362 SL won't install the modded firmware

Hello!

I have a FB 7362 SL. The original frimware was 6.03 I think, then I updated to 6.5, becouse I think it will resolve my "DSL verbrochen" problem, then I read that I should install the modded firmware, to change the DSL to Annex A. I loaded the modded image file in the FB, in the bottom left corner shows the %, it was uploaded to 100%, but after turn up some picture, and is written "das update ist fehlgeschlagen, die eingegebene datei enthalt kein von AVM..."
What should I need to do that I install that modded firmware?

I tried also downgrading to the 6.3 version, maybe then will update from 6.3 to the modded 6.5 what have I downloaded form this site, but when I want to downgrade to 6.3, I stucked when the software search for the IP, I mean when I plug the power cable in FB... I downloaded the exe file for downgrading from AVM site, i follow the tutorial, and when it says that plug the power cable in FB, then I plug, but after that it search for the IP forever.

I have the same problem - cannot install the modded firmware. Did you resolve it?

I successfully downgraded using 6.30 recovery from AVM and then was able to flash the International 6.50 NAF-MOD from the repository