Is not knowing where one's maternal aunt lives, checking on her, or communicating with her, due to the mother not providing information about her, even until her death, considered a severing of kinship ties?

Maintaining ties with one's maternal aunt is an obligation, and severing them is akin to severing ties of kinship. If you have exerted your utmost effort and were unable to maintain ties with her, then you have fulfilled your duty, as Allah Almighty says: "Allah does not burden a soul beyond its capacity" and "So fear Allah as much as you are able." You are the most knowledgeable about the effort you put forth to maintain ties with her. If you missed connecting with her during her lifetime, then do not miss supplicating for her, seeking forgiveness for her, and giving charity on her behalf after her death, because "the maternal aunt is in the position of a mother." You should also advise your mother and your other maternal aunt to repent and seek forgiveness for this deceased aunt if they were remiss in their duty towards her.