Active IQ Unified Manager: Unable to add cluster datasource

• Active IQ Unified Manager (AIQUM)
• ONTAP 9

While trying to add new Clusters to Active IQ Unified Manager following error message pops up in a windows:

Unable to add cluster datasource. This can occur if the clocks
on the systems are not synchronized and the Active IQ Unified Manager HTTPS certificate start date is later than the date on the cluster, or if the cluster has reached the maximum number of EMS notification destinations.

server_acq.log
...
JJJJ-MM-DD hh:mm:ss,523 ERROR [default task-6] c.o.s.a.s.AcquisitionFacadeUtil (AcquisitionFacadeUtil.java:202) - failed to register EMS: : com.netapp.oci.netapp.client.interfaces.data.EmsManagerException: Failed to read the certificate due to incorrect formatting. (errno=61102)
...
JJJJ-MM-DD hh:mm:ss,532 ERROR [default task-6] c.n.s.a.s.r.s.i.AcquisitionFacadeSessionServiceImpl (AcquisitionFacadeSessionServiceImpl.java:813) - Fail to add data source for acquisitionUnitName: local, dataSourceName: <IP:NNN.NNN.NNN.NNN>, vendor:NetApp OCI Essentials, model: NetApp OCI Essentials, datasourceTypeId: 91, manual: 1, isActive: false, attrs: -- listing properties --
...

server/audit.log
...
Month. DD hh:mm:ss [:INFO]:<Server-Name>:API:in:[<IP:CCC.CCC.CCC.CCC>]::GET: Fetching cluster certificate for host <IP:NNN.NNN.NNN.NNN> over port 443
Month. DD hh:mm:ss [:INFO]:<Server-Name>:API:action:[<IP:CCC.CCC.CCC.CCC>]::Adding datasource host <IP:NNN.NNN.NNN.NNN>
...
Month. DD hh:mm:ss [:ERR]:<Server-Name>:API:action:[<IP:CCC.CCC.CCC.CCC>]::Unable to add cluster datasource. This can occur if the clocks on the systems are not synchronized and the Active IQ Unified Manager HTTPS certificate start date is later than the date on the cluster, or if the cluster has reached the maximum number of EMS notification destinations.
...