I registered Upwork just one month ago and have won only three temp jobs. During the past two weeks, I have sent about 12 proposals but no feedback even though my skills and experience seemingly match the job descriptions. Also I have found that the "send proposals" and "continues" buttons appear black instead of green, yet the system shows that my proposal has been submitted. So I am wondering whether my proposals have reached the clients or not. Hope someone can help me answer my queries in this respect. Thank you.
Submitting proposals doesn't always guarantee that you will get hired or get a chance to be interviewed, but you shouldn't give up on sending proposals to potential clients. The black "Continue" button you're referring to when you're about to submit your proposal is by design. We recently got several updates/revamped made to the system and your proposals should be sent directly to clients when hitting that button.
I've pulled a few resources that may be helpful to you. Check out these articles to help you create a profile that stands out and improve your profile title and overview. For some great tips on writing proposals that win jobs, check out this article.