I have tried to submit a proposal to a job but get this error:
Sorry, we were unable to save your application.
The client is new so that may be a factor. I tried from two different browsers.
I tried Upwork chat and the support person said to try another job! That is not helpful.
There can be various reasons why the proposals weren't saved, such as the client closing the jobs or making it private. In this case, the project you're referring to was canceled by the client. Feel free to submit new proposals.