If you are using the correct login and password for the App, double check that you aren't trying to sign in to "Canada" portal.
At the bottom of the login screen, you will see a link that either says "I sign in to the app.schoology.com" or "I sign in to the app.schoologyca.com". Make sure when you login, that you see the Canadian flag at the bottom, so you know you are on the correct page.
If you are using the website, make sure you are using https://stmaryspdx.schoology.com.
If neither work, go to https://stmaryspdx.schoology.com and select "Forgot you password".