Submission link no longer working for someone

I have a form that people typically work on for months. Recently, someone who had a link says theirs no longer works, and they can't get back to their form. I have all of their forms on my end, but how do I help them get back to the editable form that they have already started?

Do you mean to say that submission edit link for users are not working anymore? 

The most likely cause for an edit link to not work is the submission must have been deleted. I do not see any reason why edit link will not work if the submission is not deleted. I would suggest you to please share the edit link URL and we will take a look. 

We will wait for your response.

https://www.jotform.com/edit/3780136142393741045

This seems to be the link...

I can see the users' data on that edit URL. You can share that to them.

They have to go through the pages by clicking the next button to see the data.