Well, you could be the best partner ever, but if your partner doesn't put any effort into the relationship, it doesn't matter.
So, I think the first step (and most important one), is to see if you and your partner are willing to keep the relationship going.
Then, you have to identify the problem in it. Maybe there isn't healthy communication, you could try to talk about this with your partner and ask them if there's anything bothering them. Try to talk about the issues you feel and they feel.
If you do not spend a lot of time together, you could try to find time in your schedule and do something fun that you both enjoy.
And... there are plenty of things that could be an issue, so I cannot give advice for them all.