Hi all,
Just to flag that the only solution I found was to delete the app, create an entire new project, replicate the code, and publish this new app under new name and new project into shinyapp.io, while deleting its previous iteration. Not very helpful as I did not understand what changes led the original app to stop working in the first place, given the code is absolutely the same. I reckon it had something to do with the project environment itself, but this is largely uninformed speculation.
Thank you