Running Safari on MacOS (latest) I see in the console:
[Error] Could not connect to the server.
[Error] Fetch API cannot load https://xp-qa.apple.com/report/2/xp_amp_web_perf_log due to access control checks.
[Error] Failed to load resource: Could not connect to the server. (xp_amp_web_perf_log, line 0)
[Error] Could not connect to the server. [Error] Fetch API cannot load https://xp-qa.apple.com/report/2/xp_amp_web_perf_log due to access control checks. [Error] Failed to load resource: Could not connect to the server. (xp_amp_web_perf_log, line 0)
Looks like a beta bug.