Thank you for
reaching out on the community and telling us about your issue. I do apologize for the issue you're having. When you try signing it does it say that your account does not exist? Does it crash when it opens or maybe it doesn't load? We'll just need a bit more information to figure out what exactly is going on.
To start off here could you take a look at the troubleshooting article down below. https://www.quicken.com/support/troubleshooting-quicken-mobile-companion-app
If you're able to find something that's similar to the issue you're having try it out. If not give us an update and we'll see what we can do!