Hello and a belated welcome to Flyer Talk!

The newly revised wiki for the thread suggests waiting 3 or more weeks before considering this to be a failure of the credit posting, At 18 days you are admittedly close to that threshold, but it's also true that the timing of Amex credits has become longer and more unpredictable than they used to be.

Personally, I would wait a few more weeks to see if it posts before considering whether to call Amex. I say this because (1) there are other data points in this thread of charges made in 2023 receiving still credits in 2024; (2) as a general matter, there have not been many -- if any -- reports in the past few years of people's credits for TB purchases not automatically posting, albeit sometimes with a delay; and (3) if you raise the issue with Amex, there is a possibility that the human you interact with could determine that TravelBank is not an eligible expense to be reimbursed according to the published Amex rules for the credit. Others may have different views.