Hi PatienceH,

Sadly few people are good at keeping in contact so it's almost certainly nothing to do with you. Even when people really mean to keep in contact life gets in the way.

I agree with the Skeezyks, the best way to combat loneliness is to get involved in something other people do as well. It could be volunteering or a hobby or interest group or club.
Initially it will feel like you're on the outside of this group too, but persistence over time (can be a fair amount of time) will lead to a gradual integration and acquaintances will become friends.

I am lucky, I have a lot of acquaintances and a few friends from activities I do and I value both.

Good luck!