Fiverr is optimized for Chrome, so if you aren’t having trouble in Chrome you could just stick with it. If you are having trouble in Chrome too or if you want to try something on the other browsers, clear all cookies related to Fiverr, all cache related to Fiverr and restart your browsers. (You can clear ALL your cookies, cache, history instead if that’s easier.)
After browser restart, navigate to the page you wanted via the Fiverr site instead of using a bookmark. For most people, this resolves any 403 errors. Those seem to often be caused by using bookmarks to go to certain pages and/or having cached data that interferes with current data.