All verification links in emails only work for 24 hours. If it is no longer active, you must register again for an study.
To unsubscribe from a study:
If you no longer wish to participate in a study, you can unsubscribe. Log in to O4U and click on "My account" at the top right.
Then click on the "My studies" tab.
Click on "Leave study" for the study you want to unsubscribe from.
Then confirm your choice.
Do you wish to remove your account from O4U. Log in to O4U and click on "My account" at the top right.
Then click on the "Edit" tab
Click "Cancel Account".
You will now receive an email with a verification link.
If you click this, your account will be removed from O4U.