Every year there are dry periods in which no reimbursements are made, and then they catch up. We don't know why. It could simply be that they need the IT capacity for something else, or it could affect someone's bonus.
It's also common for transactions made on specific dates to be skipped. If you wait patiently they will likely be picked up when they run another type of process.
I remember reading here last year at the end of November I think there was a day that was skipped. Did those people eventually get reimbursed without calling? I don't mind if it takes longer, but unsure what to do if it doesn't get reimbursed at all.