I'm glad you got it working. The 150% setting is actually the text scaling size, not the screen resolution, but the important thing is that you found that changing that to 100% got the App Manager to work and then it stayed working when you set it back to 150%. That may help other people in the same situation, so thanks for sharing this!
Also, I'd recommend creating a Windows system restore point that you'll be able to go back to if the problem shows up again for any reason. The brief
article shows the steps.