If the SQRemote <-> SQBlaster connection is working, and the Vera <-Plugin-> SQBlaster connection is showing as "down", then my first guess is that you're running DHCP and a new IP Address was assigned to the Blaster.
SQRemote uses mDNS to automatically discover where the Blasters are, but this functionality doesn't exist in the Plugin. Instead, you have to manually configure the Plugin with the IP Address of the Blaster.
If this address changes, then the Plugin will point to the "old" IP Address, and it will look like the Blaster isn't contactable (aka "down").
It would be worth checking if you allocated a Static DHCP-assigned IP address mapping to the SQBlaster within your home's router.
... but that's a guess...