What version is your software? New vehicles often come with "odd" factory versions that might have recent/special changes that don't exist in general release versions, so that can prevent updates until the special changes merge to a newer general release. It's not uncommon for people to wait a few weeks to get any software update let alone a FSD Beta update.
The current FSD Beta release available to most people is software version 2022.20.19. The first number is the year and second number is week of the year, and generally Tesla avoids "downgrading" software similar to the previous point about your vehicle might need special / newer behaviors that don't exist in the older versions.
Even today, FSD Beta seems to be adding additional vehicles that meet the requirements including 80+ Safety Score, 100+ Autopilot miles as well as compatible software version (recently seems to be 2022.20.7, 2022.20.8 and 2022.20.9). There are plenty of people who are still waiting to be added because their vehicle is on newer versions, e.g., 2022.28.2, 2022.36.6, 2022.40.4.
The next FSD Beta release seems like it'll be version of at least 2022.36.15, so currently this would likely prevent those on a 2022.40.x version from getting added when Tesla is ready to move it from limited testing to wider testing.