23h2 solution upgrade

Performing the 23h2 solution upgrade which is fine until it gets to the "Install the update orchestrator agent" step which it fails saying :

Type 'Deployment' of Role 'AgentLifecycleManager' raised an exception: Failed to complete deployment of ALM - Failed to complete deployment of ALM on servername - Adding ALM's virtual account to local admin group on servername failed. NT SERVICE\AzureStack Agent Lifecycle Agent is not added to local admin group on servername. Error: Get-LocalGroupMember : A local account with the SID 'S-1-5-21-4179914148-1131336781-1852958950-43737' was not found.

I've checked and the above SID is there already and so is the lifecycle agent account.

thanks