project.microsoft.com: We couldn’t open your project (Correlation ID error)

[RitchieP]

Hi, I'm getting this error while trying to open a project in Project online. 

I am the manager of this project; and have a Project 1 license assigned:

We couldn’t open your project.

Return to Project Home and try opening it again.

If you contact support, you can give the following information to the support agent. Correlation ID: a7a8a8ed-a909-49a3-a963-e4e11fcd528f

Thanks for your assistance and knowledge!