Could it be because you have changed some capabilities?
You are welcome to try things out on our Moodle Sandbox demo site. It resets on the hour, every hour, so it's good to log in say at 5 past the hour. You can log in as an admin and change capabilities or other settings, then in a different browser log in as a student to check how things are.
At the end of the hour, any changes you made on the site are erased, so you can try something else the next hour, or leave the site for others to play with!