I am seeing the percentage impact but why is the p-value and error margin unavailable on my metric card?
If your experiment is in its very early stages, each treatment may have only been exposed to one user. If this is the case, the p-value and error margin cannot be calculated. A t-test requires at least two data points per sample per treatment to perform an analysis. However, you will still be able to see the percentage impact on the metric card. Please note the number of users assigned to each treatment will be indicated on the live impressions tab as well as the treatment selector on the metrics impact tab.