The thing that's so hard about relations with people is that they look like they're interacting, having a great time, when they may be feeling the same way you are.
One thing I do to try to reach out is to say a nice hello to two or three people, making a comment about the weather or something else that is going on. See what kind of reply you get. Build by having a sentence or two conversation about that topic.

Or if there is someone on staff whom you have respect for, ask them a question about something work related (not too personal), asking for their insight or how they feel about something going on. Many people open up if they feel they can assist you, or if you are interested in their opinion as an equal professionals.

Then each time you see that person, if they have responded positively, do the same thing but either add to the topic (Remember when I was a kid, I'd enjoy ...... when it was like this) or pick another topic, making a little comment about that. See how it goes.
You may find you will have built a communication bridge; people will expect to talk with you. I have found they will respond when I reach out especially if I put forth a little effort. See if it feels like you are making a connection; then build on that.
If people are used to not expecting to have a conversation with you, they may feel that you're quiet and they are respecting the "do not disturb" emotional sign you may have inadvertently put out. Begin by gradually changing their expectations of you. You should make connections with others and the whole world may open up to you.
If you are at an event and you see someone you work with, say hello. Later at work, you may use that as a bridge topic to a conversation.
I think you may have interpersonal skills that have grown rusty. I wish you a brighter future with joy, laughter and friends in it!!