Its a little concerning that you had MSM and have now lost it. There's no need to load a cure fw if you have MSM, but there is every reason to load it if you haven't got MSM.

Method 1 uses [Only registered and activated users can see links. ], not Updater.exe. Maybe give it a try with WU. If that still fails and so does Method 3, then:
Method 4: Extract Garmin.rar directly onto a clean microSD. Insert into the nuvi. Extract 113201000390.rar somewhere convenient, Desktop is fine. Inside that rar folder is 113201000390.rgn and Updater.exe, drag the rgn file onto Updater.exe to open the GUI, enable the Radio button for 'USB Device'. Put the nuvi into pre-boot normally connecting to PC and press 'OK' on the GUI when the unit's details show in the window and wait. The unit should then reboot automatically and 'Loader' should appear on the screen if the firmware update flash starts.

Spoiler: Click
[Only registered and activated users can see links. ]
[Only registered and activated users can see links. ]