Failure to open project. Starts download , goes to 38% then says unknown error

[Dolbaden]

When I try to open a recent project there is a delay then its starts download and reaches 38% then says unexpected error and stops. What can I do?

[Steve Grisetti]

Are you opening the project in the same version of the program you started the project in?

What operating system do you have? Which processor do you have with how much RAM?

And, very importantly, how much free, clean space is on your hard drive?