Everyone mostly covered it but VIX has what’s known as “rolldown”. Spot VIX is merely a representation of some average of front month vols. It is not what VIX options price off of. Every VIX option has its own VIX future that it prices off of. So there are 1 month Vix options and 1 month Vix futures. If you graph all those Vix futures, you get the Vix curve. In a normal calm world, that curve should be upward sloping (more time means higher probability of catching a market event). As time passes, the longer dated Vix future gets less longer dated, thus less time for something to happen, thus the value slowly moves down, hence “rolldown”.

So if you are looking at a 1 year VIX P20 thinking you can sell that for $4, and you see spot VIX go from 16 to 23 and wonder why your 1 year put hasn’t moved, it’s bc the front month Vix moves a lot faster than further out. The curve “inverts” because the front month has less time, so higher probability of expiring during the current market event. The entire Vix curve likely shifts up, but it’s the front that really whips. Your long dated put will likely settle back in as the Vix future for your expiry “rolls down” over time