Did you manage to practice one of the versions of the body scan every day?
Remember that it's much more important to practice the body scan on a regular basis for any length of time, than it is to do the full version less regularly. It's great if you're able to do the 30-minute or 40-minute version at least occasionally, but as long as you're doing it every day, or almost every day, you'll learn and benefit from this practice regardless of how long your meditation is.If you weren't doing it on a regular basis, or even not at all, try not to be discouraged. Like anything new, many people find it difficult to get started and make a habit of it, so it's not unusual to not have done the practice as much as you'd have liked. Meditating for 40 minutes can seem overwhelming, and it would be a shame if that expectation prevented you from doing the meditations or continuing with the program.
So start with 10 minutes if that's more comfortable, and then once you've gotten in the habit of doing the meditations regularly you may wish to try meditating for longer, but if you never spend more than 10 minutes on the meditations, that's fine. Doing 10 minutes of meditation a day throughout these eight weeks is going to give you all of the experience and practice you need to learn mindfulness, get the full benefits of this program, and make substantial changes in your life.
Here are some things you can try that will make it more likely that in the coming weeks, you'll be able to do the mindfulness practices more often.
Make sure you have everything you need to do the meditation ready to go in advance. If you need to go searching for a pillow or mat, or search to find where you've saved the mp3, those are just more obstacles that will make it harder to get started.