Hi. A while ago my seat preferences disappeared and the flight was showing as no seats available for preference. I spoke to Virgin cs while checking out something else and was told that it will be because all the available seats for preference were gone and this wouldn't now change until olci. I've been checking pretty much daily for the past month or so (sad i know!) and today there are about a dozen seats available again dotted around the cabin. Could it have been a potential aircraft change and now they know which config it's going to be? If so I wouldn't have thought there'd be so few seats available as its only changed today and I would imagine everybody else's original preferences would have disappeared at the same time as mine did. I'll keep checking daily but it seems a bit odd.
Only 60% seats are available for pre-selection and once that is reached the seat maps become available. While the official line is that seats are not released until OLCI, there are occasions when seats may become available although this is rare. You do not say when you are travelling or where you are going but the possible scenarios are people with fully flexible tickets or reward seats changing their plans or indeed an aircraft change.
There was also an issue earlier on where all PE seat requests were lost because of a technical issue and they could not be retrieved. The seat maps became available again and people were able to reselect and that may be the reason for your problem.
Finally, although the remaining seats (with the exception of exit and bulkhead seats) officially do not become available until OLCI opens, the reality is that they can open up earlier so keep on checking