Smart Control Center does not discover Prosafe GS724T v3 switch - cannot update firmware

I have a GS724Tv3 switch and are trying to connect to Smart Control Center. Discovery fails to detect. I wish to upgrade firmware which I understand needs to be done from SCC, web login does not offer this option...

 

Based on research & troubleshooting so far I can advise:

• PC running SCC is connected directly to the GS724t. The GS724t is then connected to my internet gateway
• The switch and PC IP settings are correct, being on the same subnet, have same subnet mask and gateway.
• I can access the internet from the PC
• I can log into the switch from a browser on the PC and check or change any settings
• The switch is running Boot Version 5.0.3.2 and Software Version 4.2.1.5
• The PC is running W10 Pro x64
• In case of firewall blocking SCC access to the switch I have turned Kaspersky firewall off.
• If I run the command    netsh advfirewall show allprofiles    all profiles have state = OFF

I've run out of ideas at this point. What next?