Q: My mac book won't let me open any apps

Hi Ravpalmer92,

I understand that you are having multiple issues with your Mac after it powered off. Let's see if we can figure out what is going on. 

The first place to start is to see if the issue is replicated in another user. Take a look at the first article to go over how to create one and then test out the same apps and make sure that your Mac stays connected to the internet.

Mac OS X: How to troubleshoot a software issue
https://support.apple.com/en-us/HT201516​

Another thing to look over is verifying your start up disk. This is something that will be helpful because of the the sudden power off that you experienced. It will ensure that your startup disk does not have any issues. Take a look at the second article to go over how to start up in Safe Mode to verify that your issues do not happens as well as using Disk utility to verify your hard drive. 

Resolve startup issues and perform disk maintenance with Disk Utility and fsck
https://support.apple.com/en-us/HT203176

Let me know if this helps or if you need further assistance on this issue. 

Have a good day