I'm on the gamer plan. I hadn't used my sky computer for a number of months and had built up a chuck of credits on my account. Then over the Christmas period I started using it in ernest and whittled it down. It was then I notice that my monthly billing date is on the 6th of each month. But I didn't get any new credits allocated to my account then. I don't know about other months as I had not been using it for a period of time, but I know for sure that I didn't get my 80 credits for January, that the gamer plan should be adding each month.
When I look at the account page, it says "You'll receieve 80 SkyCredits on 09/19/2016". Clearly this is well in the past.
I tried to get support via the chat window on the account page. However I've had no response and that's coming up for 5 days since using the support chat channel.