You might have noticed Tom holding ayellow balloonwith a "%" icon on it. This happens when Tom has a special offer for you, so that you would be able to hire him with a discount.
This offer is validonlywhen Tom holds the balloon.
If the buttons with the hiring options aregreyed out, it means that the offer is over (and the balloon flew away). This is an unfortunate case and it can happen in a couple of circumstances:
A.if the offer ends the very same moment you tap on Tom;
B.if the offer ends while the pop-up with the different hiring options for Tom is open (before you actually hire him).
In both cases, you will have to close the pop-up with the hiring options. The discount will not be available this time, but Tom is generous and he might make a new offer if you hire him!
In this image, the balloon just flew away (on the left). The offer is over. The hiring options are grey.