Same issue with my 12Pro Max. None of the 3rd Party Apps were loading. I let the phone sit over night, several times, to no avail. I tried stopping multiple ones running at the same time, then just running one at a time, didn’t work. I reset the phone, started the import process again, a few more loaded. Even used a lightning cable from my IPad to the 12PMax. Still same issue after reset. I then uninstalled several of the apps, and reinstalled from the App Store. This worked well and remembered my settings / password on many of them. The ones that remembered my passwords were ones that I attempted to download initially.