It shows no review queue available for you, why is that so and when can I expect them back?
Just for reference, I haven't been reviewing much lately.
Not all users have access to all review queues at all times; this is the systems way to inform you that currently you cannot access any of the review queues. That bit was likely in a way obvious, but bear with me.
A few reasons why you cannot access the queue:
As mentioned in comments by amWhy one can be suspended from reviewing and historically this was indicated like this as I explained here earlier https://math.meta.stackexchange.com/a/30073/ However, as Matt mentioned this changed very recently (see Improved experience for users with review suspensions) and nowadays you would receive an explicit indication that you are suspended. That is, you are not in this case.
If you have exhausted your votes for the day you are blocked from reviewing at least in certain queues too. (I am at this point not certain regarding the exact restrictions, that is which votes block which queues.) From deleted comments it seems that you were in this case. It could be that it is also shown when one exhausted the 20 posts limit in all the queues, I am currently not sure about that.
You do not have enough points. One needs to pass a certain threshold of points to have access to the queues, which is not the same for all queues. However, for users that do not have access to any queue at all the button is not even shown, thus usually you will not see this in that case. However, on the meta site, where not all queues are available, this is shown for users that have access to some yet not all queues on main.
There may still be other cases but that are the ones that came to mind.
The indication will go away once you can again access the queues; in the case of missing votes this means usually the next day. (There can be corner cases I think, as some votes are 'restored' upon delete, but that's likely a detail and I am not sure how the logic interacts.)