There are good suggestions in the posts. My wife died 4 years ago and I find that it can be lonely even when your are around other people. But we are all responsible for ourselves and our happiness. So it is up to you to motivate yourself, (by what ever method it takes), to seek out people of like mind and interests to interact with. Volunteer at any of the programs that interest you. Be a coach for a team. Mentor someone. Work on a political campaign. There are Meetup groups, (find then on the internet), in your community for all sorts of activities - pick one or more. Take a class.
What you decide to do will be up to you. It is easy to do nothing. The less you do the loner you become. So go out and do something.

I like being alone and I embrace my solitude, but you are likely asking about feeling like nobody cares about you, appreciates you, wants to share meaningful company with you. I've felt like that in the past, and it's depressing. I just ride it out knowing that my life has its ebbs and flows.

Sometimes I feel too wanted, everybody wanting something from me and I have no time for myself - and then there are times when I feel nobody appreciates me. I'm too shy to contact acquaintances, maybe afraid they will reject spending time with me, because they have significant others or whatever. I don't like begging for attention, so I end up spending time watching movies or listening to music until the loneliness passes.

Joining a social meetup helps create new acquaintances and maybe activity partners. Hugging children or pets help with the physical needs for hugs. I'm lucky I live in a very huggy environment, where everyone hugs no matter if mere acquaintances or best friends.

I embrace it.

Watch some live music, where there is dancing, and/or karaoke, and Talk to strangers! There is always a. Ccomment about the dancers or singers (nice ones!!!) to be made.
Very soon, whenever you walk into a place, even a new one, there will be familiar faces who will be happy to have you sit with them.
Same for hikes, gaming together, birdwatching, crotchet
Just take that first step, soon your calendar will be full, and you will need naps, like I do!