After deleting the Availability Group, we will need to remove the nodes from the WSFC Cluster and, surely, it can be done by uninstalling WSFC Failover Service (instead of destroying the Windows Cluster which cannot be possible in this case). Having done that, we have to create again the Windows Cluster putting each node inside. Finally, we are going to be able to set up the AlwaysOn Availability Group. Ideally, it is the normal procedure for it.
Nevertheless, we cannot play by the procedure as each case is particular (and this case really is). It might not be a great surprise if we get this error while trying to set up the AlwaysOn Availability Group:
Obviously, this error is due to incorrect uninstallation we had done above and, luckily, to fix it we will have to disable AlwaysOn Availibility Groups feature at database engine service level.
Now we have to enable it again and then restart the database engine service
Not until you have done these all steps will you be able to create again the Availability Groups you want to. Thanks for reading again!