The Release button for your Evaluation Group is greyed out, preventing your other evaluators and reviewers from starting their scoring.
The most common reason why you may find yourself unable to release your evaluation groups within your Project is if it's a Best Value project. Best Value projects only permit one evaluation group to be released at a time. Once the first evaluation group has been withheld, the following evaluation group can then be released.
If you would like to continue running your project using Best Value standards, withhold the first Evaluation Group when they have completed their scoring, and then release the next one.
If you want to be able to have all Evaluation Groups conduct scoring at the same time, you can disable Best Value for your project via the Details page --> Actions --> Edit Project.