Hi, that was exactly my story one year back, and I was frustrated and disappointed at the same time. But, all I did was "Keywords Research and Competition Analysis." This has helped me choose the right keyword to target for my gigs, and after modifying my gigs, I got back into rankings after a week.
Note: At first, I tried targeting low-competition keywords and started ranking for those, and once I started getting orders on those keywords, I pushed my gigs to high-competition keywords.
But, these days, fiverr has become so competitive, and you need to care about dozens of factors. Nevertheless, we can give this a try; who knows, this might work for you as well.
Good luck!