Where is Earth?

In 220 AT (2269 AD), humanity had re-established itself after the exodus that it had the resources, manpower, and technology, to begin a return mission to Sol; to recover what, if anything, was left of humanity, and to bring them to the Commonwealth. Although the state of the planet was in all likelihood even more dire than when the Exodus began their century-long interstellar journey - climate and habitat predicts expected a total environmental collapse with the decade after the expedition left - there was still hope that there were those who, through hardiness or luck, had survived for several generations and could be brought to the safety of the new world. This idea had been a prevalent one since the first colonists set foot on Centaurus; the expedition, whilst costly, was never intended to be the only vessel sent out. But, as the years turned to decades, no other vessels came from Sol. As such, the people of the young Commonwealth thought it was their duty to prepare and carry out a pilgrimage to their homeworld.
Such a feat wouldn't be practical if it weren't for the invention of the Glide Drive; this drive would allow a vessel to travel the interstellar gap between Alpha Centauri in only around 15 years - a massive decrease compared to the initial 80+ year journey undertaken by the Ark. Furthermore, one of the many technologies reverse engineered from Crash Site Apollyon and enhanced by human research was better Cryogenic Sleep methods. This meant the entire crew of the mission - and the people of Earth they found - could sleep through the entire journey back to controlled space without the massive effects of prolonged low-gravity living, the massive costs of having to build the kilometres long centrifugal drum, like how the Ark was constructed, or the temporal effects inherent to high subliminal velocity travel.
After numerous years of careful selection, training, and fine-tuning, the first expedition back to Sol, named Terra 5 (as the first 4 missions were used for testing purposes, to better prepare for the dangers of interstellar space), was launched on Landing Day - the day when the first colonists made planetfall on Centaurus nearly 70 years before - 220 AT.
20 years later, the mission was declared a failure, with the spacecraft involved, the CSS Terra, lost with all 1200 hands.
The engineers and scientists involved in the Terra 5 mission made this declaration after losing contact with the Terra; even when incorporating light delay. The last message received was a standard message - the current distances from Proxima Centauri and Sol, the current speed of the vessel, and the stage of the mission. Sent approximately 15 years into the mission, the last message showed that the Terra was performing its deceleration burn as it entered Sol. Judging by its distance, it was just passing through the orbit of Pluto - although the planetoid was on the far side of its long elliptical orbit at that time - at the point of its last transmission.
This outcome was a worrying one. The computer systems aboard the Terra - although adhering to the Commonwealth's strict AI Safety regulations - were advanced, and in the event of catastrophic failure, the entire crew could be woken up automatically through an independent subsystem. The fact that no messages from the crew were ever detected suggests that this system failed.
Since then, theories have been proposed from both rational and irrational sources, ranging anywhere from a freak but awful accident mid-transit, a redirection by a rogue planet in the interstellar void, or even that the ship was intercepted by elements of the Tarrasque navy - unseen since they abandoned Earth at the end of the 21st century AD - and had been captured/destroyed/probed by them. The most widely accepted narrative is that a freak accident caused the destruction of the Terra; however, due to the sheer number of lives lost - at that point, it was the single most amount of lives lost in one accident in space - and currency sunk on the project, calls to send a second mission to Earth have been met with mixed responses. With the growing anti-Earth sentiment from rebellious colonies on the Frontier, much of the population of the Commonwealth don't see the value in returning to our home. "Let the old worlds die," some may say.
Others, however, would always argue that we should not forget what we left behind.