Check your authentication service availability on those services.
For on-premise authentication services (such as LDAP, Radius, or Kerberos), you
can review audit logs for incoming user requests or login errors. If there is a
lapse in incoming requests, take packet captures on the relevant network
path.
For public authentication services (such as SAML or cloud LDAP or Radius
services), review audit logs provided by your authentication service. If there
is a lapse in incoming requests, check with your authentication provider for any
ongoing outages.