Hi Kim, thanks for informing me about it. Maybe you are using the latest wave of UKHLS wave 10? CPF v.1.1 is not yet updated to the versions of data that were released in 2021. For UKHLS, it works on wave 9. I think this may the reason for this error. However, incorporating new waves for UKHLS should be fairly easy (see the Manual, code updates are required in the high-level syntax to define the number of waves). If you figure it out, please share the code so that others can benefit from it.
Unfortunately, CPF has currently no financing and staff to update the code on regular basis. However, we believe in the community-based effort to progress it (an open-source code social experiment!). One way or another, updates to the code can be expected in Autumn.
Good luck with your research!
Konrad