Yes you will have to re-do the skills sessions or intro ride I'm afraid. These last for 6 months (in the same way that someone leaving the club would have to do the skills session/intro ride if their membership lapsed beyond 6 months).
I have a spreadsheet of those who've attended all the sessions but people are removed after 6 months has lapsed and as they say... If you're not on the list ;).
I'd normally have sent you an email explaining this by now but I'm on holiday in Cape Town at the moment and our internet seems to only work for about 5 mins at a time so have been trying to process membership stuff whilst I've been sat in a cafe with Wi-Fi! Fun and games!