What are the reasons for an agent receiving an unacceptable grade?

What are the reasons for an agent receiving an unacceptable grade?

A device can receive an unacceptable grade for two main reasons:

1. When the total response time surpasses the configured threshold, resulting in an Apdex score of 0.48 to 0 as an unacceptable grade.
2. If the associated application is unreachable due to issues such as an invalid URL, IP, or host