Comichorn published DC's sales ranking for January (The ranking are separate from Marvel and there are no numbers of units sold) -
https://www.comichron.com/monthlycom...2/2022-01.html
While there are no concrete numbers, it does seem Robin slightly dropped in the ranking (although some books started new arcs and there were a few #1)
I know that numbers are definitely tricky right now, and Robin will probably get a big sale boost next month because of the big crossover event with Batman, but overall it's still a bit surprising, as so far the run has been very good.