I'm not getting sustainable money for my products

It has been said the only real product validation is to charge people for money, so I tried to monetize in a lot of different ways, but none of them gets me anywhere very far.

Long story short without getting too detailed into the product, I tried things like

• Adding payments to every product that I have on my website, like on 3-4 features
• Changing the pricing model to subscription so that I could get recurring revenue per month
• Different marketing channels, like FB ads, Google ads
• Post the products on public forums, multiple times per week
• Talking to every personal connection I had trying to sell the product (the product is a marketplace so it has a B2B side as well)

I'm getting little revenue from doing all these effort, and starting to lose motivation on continuing. I felt on the 2B side, there's lacking of more connections to businesses, especially high level people who can make buying decisions, and on the 2C side, the conversion rate is very low that doesn't get me anywhere.

Am I missing anything obvious? What would be some tactical advices you might have? I could really use some pointers. Thanks!