Problem running Update-ClusterFunctionalLevel on Server 2019

Hi 

I have in-place upgrade a 2 node SQL cluster (from Server 2016 Std. to Server 2019 Std.). The whole process worked as expected.

The SQL installation is not a Always On installation, it's just a regular active/passive installation.

Now I want to run Update-ClusterFunctionalLevel, but it is returning the following error:

Update-ClusterFunctionalLevel : Updating the cluster functional level failed.
    The system cannot find the file specified
At line:1 char:1+ Update-ClusterFunctionalLevel+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : ObjectNotFound: (:) [Update-ClusterFunctionalLevel], ClusterCmdletEx
   ception+ FullyQualifiedErrorId : FileNotFound,Microsoft.FailoverClusters.PowerShell.UpdateClusterFunc
   tionalLevelCommand

I see these lines in the cluster log, when the "Update-ClusterFunctionalLevel" fails. It seems to be related to a certificate issue, but I can'f find the root cause. 

0000112c.00001910::2019/07/25-10:09:30.858 INFO  Keyname not present for ClusterPKU2U, generating one
0000112c.00001910::2019/07/25-10:09:30.873 INFO  [Cert] Added new cert of type ClusterPKU2U to the store
0000112c.00001910::2019/07/25-10:09:30.887 WARN  mscs::GumAgent::ExecuteHandlerLocally: (-2147024894)' because of 'NCryptImportKey(certProv, 0, BCRYPT_RSAFULLPRIVATE_BLOB, &nameBufferDesc, certKey.Reference(), (PBYTE)c_data(keyData), (DWORD)keyData.size(), NCRYPT_OVERWRITE_KEY_FLAG | NCRYPT_DO_NOT_FINALIZE_FLAG | NCRYPT_SILENT_FLAG)'
0000112c.00001910::2019/07/25-10:09:30.887 WARN  [DM] Aborting group transaction 47:47:1719467+1
0000112c.00001910::2019/07/25-10:09:30.887 ERR   [CORE] mscs::ClusterCore::VersionUpgradePhaseTwo: (-2147024894)' because of 'Gum handler completed as failed'

I have posted the same question in the "High Availability (Clustering)" group, but they ask me to create it here as well