According to the teachings of The Urantia Book, our system of Satania, and therefore our planet, Urantia, has been under quarantine ever since the outbreak of the Lucifer rebellion. I'll reference some passages for you, and recommend that you also read the sections they come from...
From "History of the Rebellion":
53:7.3 Upon the actual outbreak of the insurrection the entire system of Satania was isolated in both the constellation and the universe circuits. During this time all incoming and outgoing messages were dispatched by seraphic agents and Solitary Messengers. The circuits to the fallen worlds were also cut off, so that Lucifer could not utilize this avenue for the furtherance of his nefarious scheme. And these circuits will not be restored so long as the archrebel lives within the confines of Satania.
And from "Present Staus of the Rebellion":
53:9.5 Since Michael’s final bestowal no one in all Satania has desired to go to the prison worlds to minister to the interned rebels. And no more beings have been won to the deceiver’s cause. For nineteen hundred years the status has been unchanged.
53:9.6 We do not look for a removal of the present Satania restrictions until the Ancients of Days make final disposition of the archrebels. The system circuits will not be reinstated so long as Lucifer lives. Meantime, he is wholly inactive.
And from "The Jerusem Triangles":
46:8.2 When Satania can return to the constellation fold, then will come up for consideration the readmission of the isolated worlds into the system family of inhabited planets, accompanied by their restoration to the spiritual communion of the realms. But even if Urantia were restored to the system circuits, you would still be embarrassed by the fact that your whole system rests under a Norlatiadek quarantine partially segregating it from all other systems.
46:8.3 But ere long, the adjudication of Lucifer and his associates will restore the Satania system to the Norlatiadek constellation, and subsequently, Urantia and the other isolated spheres will be restored to the Satania circuits, and again will such worlds enjoy the privileges of interplanetary communication and intersystem communion.
About the "Wisdom of Delay":
54:5.1 Of the many reasons known to me as to why Lucifer and his confederates were not sooner interned or adjudicated, I am permitted to recite the following:
54:5.11 10. The Divine Minister of Salvington issued as her third independent proclamation a mandate directing that nothing be done to half cure, cowardly suppress, or otherwise hide the hideous visage of rebels and rebellion. The angelic hosts were directed to work for full disclosure and unlimited opportunity for sin-expression as the quickest technique of achieving the perfect and final cure of the plague of evil and sin.
There are those who claim that they have knowledge that the Lucifer rebellion is settled, and that the system circuits have been restored...maybe you have heard such claims. It is tempting to think that we might be living in an age when the system is being restored to normalcy, but to me, after reading the above quote while observing the world in which we live, it is amply evident that we are still in a time of "unlimited opportunity for sin-expression." I can't help but think that when the adjudication is completed, the celestials will make it known to the worlds in such a way that we won't have to guess whether it's true or not.
I suspect it will be quite awhile before enough beings from isolated worlds (like Urantia) in our system 1) know about these important pieces of universe/planetary history, and/or 2) when enough of us have made the final choice for God over rebellion. Only then will our system be safe enough to be restored to the family of planetary systems as an equal and participating member. Again, it is the entire system which has to be restored—and even then, each world that participated in rebellion will have to be considered for readmission. I think we have a long wait before this readmission can be realized. Until then, we must soldier on, doing our best to help those of our brethren who still sit in the kind of spiritual darkness that was the result of the rebellion—help them come to know God and choose his ways of truth, goodness and beauty.
Thanks so much for your note and question. I hope that this reply has been helpful.