Hi Haozheng, I'm glad you are enjoying my work. It's a shame that the payment options provided by the platform are not working for you. I assume you already tried both PayPal and card payment... if you have some other available at hand, did you try a card from a different bank?
As you pointed out, there are already some packs also available on Unity Store. However, to publish things there I need to prepare the assets specifically for that software (which takes time because it requires quite a lot of additional work), plus the fact that to publish anything there it has to be manually revised by a person, and because of that the waiting queues are usually longer than a month. Unfortunately, the collection will be released there little by little, I'm unable to just go a publish everything there in a click :(