On some platforms, such as TOS, MQ VBT may disappear from the charts when viewing an index, like SPX. You can confirm that MQ VBT is still added to the chart via the Edit Studies dialog, even though it’s not showing up.
The reason this happens is because SPX really isn’t a stock like AAPL. Therefore, it doesn’t have volume and other characteristics that MQ VBT requires. This prevents MQ VBT from appearing on specific symbols like these.
To have MQ VBT return, change to another symbol, like AAPL, and you should once again see MQ VBT appear once again.