Situation: Rolling pool upgrade was greyed out for the two XenServer 6.0.2 hosts I had in a resource pool. The option to tick and select them all existed – but wouldnt ‘stick’
Solution: Simple one this one – it was more me being dense. Need to make sure your XenCenter console is first upgraded to the new version. (I though I had already performed this, but the admin machine I was on had its snapshot reverted!) The console will not tell you there is nothing to upgrade or that your xencentre needs to be upgraded.
Upgrade XenCentre Console on my admin box to 6.x
Mount CD and setup NFS share for data / XenServer 6.x upgrade
Open the XenCentre Console and select Tools > Rolling Pool upgrade
Select the servers – FINALLY progress to the next step!
This was the top article in Google for the issue I was having (Upgrading XS and having a grey’d out issue). While this article can fix an error, another possible issue (one I had) is that your server license has expired (or there is no license). You need to license it first. Figured I could write a second article or just add to this article that I found very helpful. Hope this helps!