Symptoms
Customer panel is unavailable, but the provider login works.
The POA debug log contains:
Jan 27 21:20:07 pemosscore001 : DBG [UI:pre-login:2710572:1422393607279 1:9440:2008 lib]: [Plesk::AA::PEM_Current::check] {module_id="Common"; code="210"} Access to IDL:Plesk/SecurityManagerPrivate:1.0::registerLogout attempted under slave node account. Slave node account grants permission only to restricted number of methods. UI:pre-login:2710572:1422393607279
Jan 27 21:22:07 pemosscore001 : DBG [UI:pre-login:2710630:1422393727281 1:9008:b2c lib]: [Plesk::AA::PEM_Current::check] {module_id="Common"; code="210"} Access to IDL:Plesk/HostedServices/HostedServicesPrivate:1.0::registerLogout attempted under slave node account. Slave node account grants permission only to restricted number of methods. UI:pre-login:2710630:1422393727281
Cause
The UI service is not processing requests, the reasons of such behavior can be different.
Resolution
Please contact Odin Technical support in order to find out the reason of hanged UI service.
As a workaround you can restart pemui service as described in https://kb.cloudblue.com/en/4642.