Try evoking their Higher Self, imagine yourself in a temple space and see a light form on the ceiling of that space, call “Higher Self of (their name) appear before me” 3 times in your mind, visualise them come down from the ceiling as a wiser, calmer, more generally advanced version of themselves.
First, thank them for coming and make a case for why your relationship needs to work, present this with passion and clarity as though you are appealing in a court of law for something. Don’t beg or plead if you can avoid it, and do not under any circumstances attempt to bind, compel, threaten, or moral-blackmail the Higher Self of the person.
After doing this, ask them questions, keep it to not more than 5 or 7, and you can open your eyes breifly to check a list written out, ask for example:
-
can this be fixed?
-
is it in the best interests of both of you for this to work out?
-
what actions should you take, or not take, to help things?
And so on.
This is a kind of fusion of methods from both shamanic healing work and simple magickal evocation. I think going by what people post here, this is a better Step 1 than trying to use demonic evocation/contact, but this is JMO and I am not insisting you do it, nor will I be offedned if you prefer not to. 
You may also want to check this topic: