VPN Gateway Public IP - Cannot save to static or change timeout.

Hello,

I have established a S2S VPN connection from Azure to a local Cisco ASA.  All connected and working, however I am unable to update the public IP from Dynamic to Static, nor change the Idle timeout above the default of 4 minutes.

Error:

Failed to save configuration changes to public IP address 'Gateway public IP'. Error: There was an error processing your request. Please try again in a few moments.

I have left this overnight but still experience the same issue.  

Any ideas?

Thanks.