Don't lose heart. I etch glass for sale at craft fairs. I am still doing quite well but some shows are a bust, despite a lot of advertising. A lot of times it depends on how close the nearest holiday/event is. I did well at a show just before Valentine's Day but everyone did poorly at a show in the same location a month later. But, I have had calls from the March show so got custom work out of the bad show.
I have another craft fair on Saturday, the day before Mother's Day, and hope it will be busy. It is an established show in a busy shopping mall so should do well.
Over the years you will figure out which shows do well for you and which don't. Also, ask other vendors which shows they do well at. Vendors are happy to share, as a rule.
This is my third year at this but the first year I am doing a lot of events. I am to the point that show organizers are coming to me.
But, yes, there are still shows at which I wonder why I bother.