With the JSON, you need the password if its encrypted to unlock the wallet. Your statements are too vague to come to any conclusion as to what happened on your side.
MEW allows the JSON to be uploaded and the password opened to access the wallet - although this is the least secure methods. Metamask needs you to do something else than just this.
I got my Ethereum but after some days my Metamask was crashed. I don't know why and there was a fix/repair option on it. I tried to click the repair option but unfortunately, My Metamask restarted and everything was deleted. I tried to use same JASON File but didn't work and my Ethereum went lost.
Makes no sense to me, it might be something new that happened to you because I have never heard anything similar or my facts are lacking.
Possible that you might have installed a rogue version of metamask (??) - do provide more information as to whether you downloaded the correct metamask extension and your ethereum wallet address to check on the money.