instances not starting

I am having trouble starting an app I have.
For context, I have 2 applications on a FREE plan: one application (App A) I use daily, and another (App B) I use very rarely.
Since this morning, App A does not start:

  • if I access the URL, it stays on "Please Wait ..." indefinitely
  • if I try to restart it from the console, it stays on "deploying: Starting instances" indefinitely
  • if I try to re-deploy (and start) it from RStudio, it gives me the following error:

Of course, being on a FREE plan, I can't really 'contact support'.
I have checked the usage and there isn't any overage (I am at 12 hours in the current cycle).
I have looked into the logs, but I have nothing for today.
Also, App B works flawlessly.
Any suggestions on how to troubleshoot this?