This couple is already posting as a couple. How and why do I Add Couple Relationship?
I'm thinking that a ancestor ID would be useful.
Does your couple look like this one. With the Marriage date and place?
Or does it look like this:
If it looks like "No marriage Events" Click on the little pencil to add information.
So that is my best ideas, without a person ID from your Family Tree.
The other thing it could be: perhaps your computer needs a "Delete Cookies". Or your phone app needs to be refreshed. The phone app has frequent upgrades that may alter your experience.
This is a link to a Help Article for How to I delete cookies from FamilySearch? You can find the Help Center by clicking on the ? mark at the top right of the page.
Please let me know if any of this is helpful. If not, please include the Family Tree ancestor's ID in your reply.
Thank you for the great question!