Not able to move issues from To do to In progress

[anvita.kesharwani]

In my next-gen projects users one day before were able to move issues in boards.

But today they are saying they cannot move issues from to-do to in progress.

[Esther Strom]

Is it possible that their project access changed, or that general project permissions changed?

In next-gen, there are two access points: Project Access, which determines who can see your project in general - 

And project roles, which determines what individual users can do in the project:
If you changed your project access from Open to Limited, your users would not be able to edit (or transition) tickets unless they were explicitly added to the project.

Similarly, if a group or user that are explicitly in the project had their role changed from Member to Viewer, they would no longer be able to transition issues.