You can go to Community & Help->Help and just pick ANY question. Scroll down and click the I Still Need Help link. That will open the email form. Change the subject line and tell them your problem.
If the Call Back link is available, that is probably the fastest way to contact them.
The Chat can only answer basic questions, and anything else, they will tell you they will send an email on your behalf to Etsy, so you might as well skip that step.
Many people are reporting slow sales right now, even if they didn't use Royal Mail, so I doubt that is it. But anytime you change something in your listing, it can change your ranking in the search engines for a while until the changes are noted and settle in the search engine, which can often take a few weeks.
