The most common issue with CBS is a notice attached to the CBS league.
Sometimes, when a commissioner needs to take a specific action, CBS blocks all access - including to us importing the league - until a notice on the CBS website is addressed.
If a CBS league doesn't import, please check the league on the CBS website and ensure no notice needs your attention blocking your access to the league.
Also, please note that the 2024-2025 CBS Fantasy Leagues won't be accessible until CBS opens up their 2024-2025 fantasy leagues. That is often as late as June in any given year.
Also, try this:
Please delete the CBS league and re-import it. If this doesn't resolve the issue, please delete the whole CBS account from Footballguys, log back into CBS, and reimport your league.