How to find problems that need to be solved in Ecommerce?

Before I just wanted to sell T-shirts that I think were great and I thought others might like, but I didn't know for sure if others would like them. I hear a lot that in Ecommerce or any type of business really the goal is to look for problems and find solutions but how do I do that. Is there a software I can use to see what people really want and how many people want it? I tried using Facebook and reading comments in certain Facebook groups like camping, but nothing. When finding solutions to these problems is it really necessary to invent things, I'm not really an inventor. I just want to sell people products they want, but what they want is what I am having trouble finding. Any software to help me do this?

PS ~ Is it a good idea to just simply find a Facebook group like camping and ask in a comment what are some problems people face every time they go camping? Should I also clarify in the Facebook Camping Group comment that I want to start a profitable online business while helping people buy what they want to buy. If I'm making profit and people aren't happy with my product than just simply forget it, I don't the profit. I only want the profit if others are satisfied with my product. I have been camping twice before and liked it. Wouldn't say I'm an expert in camping but I want to discover problems in that niche and find solutions, so those solutions can help me in the future as well whenever I have the time and money to go camping.