I'm sorry you're having a tough time. It can take time for some people.
Here are some things I did.
Join a senior center. I exercise there. I've taken yoga and other classes. I've participated in some social activities through the center. I made friends.
Develop a social life. I have had more fun and a better social life since retiring than ever before.
Try something new. Just because you try something doesn't mean you have to stick with it. If you don't like it, try something else.
Go to the Library.
Help at a charity once or twice a week.
Help your church with things. Get involved in a group activity through your church.
I love to mow the lawn, garden, walk my dog, enjoy the sunshine on the deck, read, and do things I've never done before.
Retirement was pure relief for me. I was happy the second I walked out of the building and never looked back. I was high enough up in a huge international corporation for nearly 40 years and saw the changes and maltreatment of employees firsthand. I used to get reprimanded for not treating my departments the same.
I admit part of my relief was that I was grandfathered into the defined benefit plan and other retiree benefits - they cancelled all of them at the end of that year.