@suman
I’m behind a simple router firewall, no changes made since months
I’ve tried to ping updates.rockstor.com which showed 192.195.81.208 with 100% loss 
Having said this, maybe this additional piece of information is worth to know…that since a while I’m also facing problems that the Rockstor forum is from time to time not available via my internet (LAN) like just now…I’ve to use LTE via my mobile 
EDIT / SOLVED:
Looked at my router which was running for more than a year without reboot - initiated a reboot and finally all issues on my Rockstor server regarding updates disappeared 
- updated immediatly to Rockstor 3.9.1 
