If you are using a guest version(free version), you might be restricted some premium features.
Guest(free) version limitations:
1. You can only open(create) up to 3 projects (But you can still participate in a project which created by another users).
2. You can't be registered as the same company(team) member.
3. Maximum file uploading capacity is 10MB per time.
4. Only 50MB of storage space is given.
5. You can only search for the contents that are uploaded less than a month. Attachments that uploaded more than one month are not available for download.