Why can't I edit this record?

The two reasons an edit is blocked — your access level, or a completed project.

Two things stop an edit:

1. Your access level

With Add & Manage Own you can change your own records but not ones other people created. Managing others' records needs Manage Team Records or Manage All. If the Edit or Delete option isn't there, your level doesn't allow it on that record.

2. The project is completed

A completed project is read-only. Open it and choose Restore / Move back to Active to make changes again.