your content is just not interesting enough
The "cool design T-shirt" market is pretty well flooded. People can easily buy T-Shits with all sorts of cool designs just about anywhere. From street markets to department stores. Even "custom made" T-Shirt sites are everywhere. You need something more original. Simple as that.
How much research did you do into niche selection? Any at all? You really should ...
1. Hit Google and Youtube up with "drop shipping niche selection" and read/watch everything you can.
2. Read all the niche selection blogs at https://alidropship.com/category/blog/what-to-sell/
3. Read the guides at https://alidropship.com/guides/
4. Finally ... do research on Google Trends and Adwords Keyword tool and even just normal Google searching to determine popularity and/or competition levels of the niche. Check out how many Facebook pages/groups there are for that niche ... ete etc
... then start again. I would. I've actually scrapped three sites that did not work and used the licenses to try something different until I got it right.
But that's just my opinion. Anyone else here with an alternative reason for the failure and/or a strategy to remedy it?
That's only one factor - i.e: how many customers are interested in them.i've researched my other niche which is sunglasses and the chart is going up on google trends