Apparently the late-posting problem for Rocketmiles is system-wide, or at least not related to whether your account is new. I set up an account in 2015 and had one stay that year. No stays since then until early this month (March 2022), when I did a one-night stay for 3000 miles (plus the 2000-mile RM boost, because I did not yet know that those would not count as base miles) and then a two-night stay for 10K miles. Both at hotels in Bangkok, in case that matters. RM sent me emails after each stay was completed saying when the miles would post: March 18 and March 20 respectively. But none of the miles have posted to my AAdvantage account, and my RM account now lists the miles for both stays as "pending". I have also had several stays using bookaahotels.com -- I started using this site instead of Rocketmiles, notwithstanding the amazingly bad interface, once I learned that both sets of bookaahotels boosts do count as base miles, so much better miles/dollar ratio if you can actually find a hotel there -- for a total of 22.5K miles, and none of these have posted either. But the bookaahotels FAQs say their miles will take six to eight weeks to post.