My profile accidentally had an incorrect hourly rate, which was below the minimum hourly rate that Upwork allows. Anyway, after the first attempt to submit application failed, I corrected the rate. Everything looks okay on my profile now, yet I'm unable to resubmit it.
Also, can't find the link to raise a ticket.
The reason why you can't submit your application is that you`re an exclusive member of the agency. If you would like to work as an independent freelancer the agency owner will need to change your status to non-exclusive. Thank you.