Sorry for the very late reply. Somehow we missed your question 😞 For browser monitors we automatically instantly retry the test and only report an error if the retry fails as well. For HTTP monitors the is currently no such behavior or option.
In the Classic Synthetic product, retry on error was indeed only for certain network error conditions but for Dynatrace Synthetic Browser Monitors retry on error is available for all failures. You can enable/ disable it in the Outage settings tab.