Based on what you are telling us, maybe it’s not moving forward because of storage issues. Try performing a master reset first, but I do not think that will help.
If that does not help, check this thread → Tutorial: Sync 3.4 NON-NAV APIM: Failure to Update to Newer Version Sync 3.4
Even though it’s for 3.4, overall is the same for troubleshooting low storage on APIM for your current situation.
Finally, since you already reformatted the unit, another easy, clean and fast method would be to force a reformat installation of 3.4.