does the spinner appear after the button click?Can you see in the browser console that the request is leaving (network tab)?
Error unbound [01234567:0] error: remote control failed ssl crypto error:00000000:lib(0):func(0):reason(0)
{"domain":"metrics.icloud.com.","type":"whitelists"}
will try to reproduce
Something must have changed from orig. 23.1
sorry, more info needed: after that the domain does not appear in the Whitelist Domains list at ui/unbound/dnsbl/index? are there any errors in the backend or general log after that?