Bournemouth breached the previous ffp rules and paid a near £5m fine - a fine being the only sanction then available - so there breach was settled. QPR were similarly punished in resect of their ffp breach under the old rules.
Mr Popodopolous will be more in the know than I, but I think Villa's situation with ffp is similar to that of Derby and Wednesday, i.e. while the sale of a stadium did not, in itself, break the rules, the EFL are looking at how the valuations were arrived at and whether they were at fair value. This is not re-opening old cases, but rather that the investigations have been ongoing ( partly thanks to the pretty inept way the EFL have handled things).
My guess is that Villa has been under the radar in the meantime, due to having been a premier league club since the season(s) in question. Relegation, if it happens, would bring them back into the EFL jurisdiction.