The canon novel Tarkin reveals that Sidious intended to continue Plagueis' research (with Vader's assistance) once the Death Star was completed, and the Empire demanded less of his attention:
The sooner the [Death Star] is completed, the sooner you [Vader] and I [Sidious] can devote ourselves to more pressing matters - matters only you and I can investigate and that have little to do with the Empire."
Save for Sidious, no sentient being in close to five thousand years had set
foot in the [Sith shrine beneath the Imperial Palace]. The room's excavation and restoration had been carried out by machines under the supervision of 11-4D. Even Vader was unaware of the shrine's existence. But it was here that they would one day work together the way Sidious and Plagueis had to coax from the dark side its final secrets.
As powerful as the battle station might become, its real purpose was to serve as a tangible symbol and constant reminder of the power of the dark side, and to free Sidious from having to portray that part.
Attacks like the one directed against Tarkin's moon base and discoveries like the one on Murkhana were distractions to his ultimate goal of making certain that the Force could not strike back
Tarkin Chapter 9: "As Above, So Below"
Tarkin is set five years after Revenge of the Sith, so evidently no research was being done during that time.
Since the first Death Star was not fully operational until the events of A New Hope, it also seems doubtful that there was any research happening in the fourteen years between Tarkin and that film; without a Death Star, and with an Imperial Senate, Empire-running must still occupy the bulk of Sidious and Vader's effort. According to the best estimates we have, the Death Star was destroyed mere days after the destruction of Alderaan.
Since Sidious is evidently delaying the commencement of their research until the completion of the first Death Star, it also seems likely that he'd delay it until the completion of the second Death Star, which he clearly intended to crush the Rebel Alliance and restore "harmony" to the Empire. Since this didn't happen, it seems most likely to me that he and Vader simply never got around to teasing out the mysteries of the Force.