Sorry to hear you're having a bit of trouble with the link! The problem is likely that your email service is stripping out the link, but no worries, you can still book a time through the platform:
1. Log into your account
2. Click My Surveys
3. Locate the project in your list
4. Click "Book Time"
If you're able to access the scheduling page but do not see any days highlighted with blue availability or receive the notification "maximum bookings met" this means the researcher does not have any more available spots for this project.
You can use the messages feature to send them a quick message that there doesn't seem to be remaining availability but that you'd like to participate! Please note, this doesn't guarantee that more spots will be opened within the project.