Bringing up a SQL Server in an isolated environment, but it was part of a Windows Failover Cluster and SQL Availability Group? It will likely be faster just to clean up the cluster configuration on the node and build a new single node failover cluster and single node availability group. (Note: you do not have to reinstall the OS, the solution is much simpler than that).
1. Start PowerShell under Administrator
2. Run “Import-Module FailoverClusters”
3. Run “clear-clusternode”
I may come back and walk through the whole process, such as first disable the Always On Availability Groups in SQL configuration manager and all that, but the above was the missing piece for me when the AGs and WFC would not respond or let me do anything through the GUIs.