I would have a few questions:
Where are you currently selling your pieces?
What marketing are you currently doing?
Who is your ideal customer?

Once those questions are HONESTLY answered then I would analyze the answers and see when you can pivot a bit. 

One of three things could be going wrong, you are not reaching your ideal market - your pricing/marketing could be off - you are marketing to the wrong market.

At Clever Cow we would do a discovery where we uncover all these and other answers (including buyer personas), analyze the answers, and come up with a plan to get you in front of the right people (including in-person events - people have a tendency to only want to move online and to the newest marketing trends but sometimes the oldies are the best).