It seems you've not been able to come to terms with the loss of your daughter some 12 years ago. Such long, constant and intense reaction to your loss would likely turn anyone into myriad health issues, mental, physical, and even social, as your state of loneliness attests to. Have you not sought any professional help yet?

I seriously hope you look after yourself in ways that make YOU less prone to these host of issues which often mean even less capacity to counter afflictions. At 80, I do everything almost daily that would ensure me live alert and independent.
The apartment bldg I live, and most condo dwellers, do NOT get to meet other inhabitants. Only co-housing and to a lesser extent, co-ops provide more contact with fellow dwellers.

But it does not mean your chances to meet the world out there is foreclosed. From community centers to libraries and coffee shops, book stores and yes the meetups, they all provide opportunities for all ages with range of interests. I, keep exploring, though I have not developed personal bond as a friend yet. Since you had such a rich life, Not sharing it with another person would be a shame -- certainly a loss for people around you.