Most couples do not have an even level of commitment to the marriage. Although both spouses would need to be willing to try, if your spouse isn’t ready to come, there are things you can do (and not do) that may help your spouse be more open to coming. There is an article specifically designed for people whose spouse is less committed to the marriage.
This article has been immensely helpful on how to interact with your less committed spouse.
Another suggestion is to let them know you are not asking them for a lifetime of marriage with you, not even a commitment of 3 months, or even a month. You’re asking them for just four days, and if by the end of 4 days they still want to end the marriage, let them know you’ll support their decision. You might want to write these words in a very short note to them. Leave it somewhere for them to find. This lessens the chance of an argument. Don’t pursue asking if they read the note, or what they thought of it, etc. Let them come to you to respond to the note. If they respond. Patience is key.