There is a report that we run often and I would like to make changes to it but it does not give me an option.
If a custom report was created by someone else you can have the creator select to share the report when they edit. Once the report is shared you will be able to make changes. As an alternative you can select to copy the report to "My Reports" if you would like your own copy to make changes.
If an admin has left the organiation and you would like for the ownership of those reports to be changed, contact support and reference this solution.