There could be a lot of answers to this often asked question, starting with "Do you have enough items in your store?", or "Are you promoting and advertising outside of Etsy?", and even "are your listings 'Relevant'?"
But right now in early April the answer very well may be warm weather!
I've had Serenity in Chains on Etsy since 2011, which is long enough to notice trends. A big one is the limited online shopping traffic during late spring and summer. During the warmer months people are more likely to send their time (and money) outside. They are BBQing, going to festivals, and spending more time away from the interior of their home (and their computer). This means a general slump in sales for those of us in the northern hemisphere.
"How do I combat summer sales slump?" Glad you asked! Selling and being in business is about constantly getting your stuff in front of your target market. This means if they aren't online, then getting your stuff in front of them physically. So think about what shows in your area that your target market would most likely frequent, and get a booth! Put out flyers (which should cost nil title more than time and printer ink) at venues that your customers may be, and network with local businesses that compliment, but do not compete with you.
For Serenity In Chains that means art fairs, NOT craft shows (our target market doesn't shop craft shows), concert venues, conventions, and networking with the local art commission and downtown restoration project.
This strategy also helps boost seasonal (holiday) sales, as people get the opportunity to touch your wares, fall in love, and beg for them as gifts!!
So don't get downed by the Summer Sales Slump, but take the opportunity to switch gears and get out there in your community and get noticed!