Here's what worked for me:
(a) I saved my proposal in a separate file so I wouldn't lose it during the process of applying for a job;
(b) Tried several times, about 15-20 apart, until it worked!
I see you were able to submit a proposal for that job. And yes, the client had certain location preferences set up for the job and they'll see whether you meet those preferences or not on your proposal. Still, they will be able to access your proposal.