Understanding Society User Support

Hi,

I am a novice at using Understanding Society data, but it is my understanding that respondents in the Covid-19 survey also appeared in Wave 9 and that I should be able to match their Wave 9 responses using their cross wave identifier. When I try to do this there are no matches (no pipd matches between the two data sets). I have no doubt I am doing something wrong or misunderstanding something but I am unsure what exactly. Can you please clear up this misunderstanding for me?

Thanks,

Chris