ews_response probe is setup, but when reviewing in UMP, we're not seeing any data displayed. The raw data shows NULL values recorded for each data point.
Monitored mailbox is full. As the probe tests the response time by sending/receiving email, it is unable to collect measurements.
You can configure the ews_response probe to delete all items in the sent items folder to free up some space. This is documented here:
Also, you should review the mailbox settings for size and retention of email to ensure that the inbox doesn't get full due to normal ews_response use.