How long does it usually take for models to sell?

Your work seems very nice and is very reasonably priced, so I don't see a problem with that. You could try some high poly models and 3d print models to expand your portfolio. January may be a slow time of year for some. With the continuing pandemic some game developers and advertisers may have slowed down. I only sell print models so I can't comment accurately on sales of other stuff, but last year January was a slow month for me, with things picking up in mid February.

Customers on CGTrader are varied, so you should offer a wide variety of formats and subjects.

Another reason may be that you aren't giving yourself enough time to build up a customer interest in your models. Look at how many views you are getting to gauge how much interest there is.

You're welcome. In addition, if you model something that there there is hundreds of, for example a wine glass, your model may not stand out. An analogy would be that the average person may not notice a new star in the sky unless it is significantly brighter than the others.

Some people may be looking for something different or specific. Its rare to find something not modeled before, but I'm sure there have been times when an artist has released something and it became a flash sensation, probably surprising the artist as well as his peers.

I still have models that have not sold once. I think iam on this platform from 2017. If i remember correctly i havnt sold anything first year. Your success might depend on things you sell (what do people need) on presentation, on how tuff the competition of that particular item is and on how many models you have in general.

Some Pointers.

1) Lose ya back grounds ya backgrounds. 9 times outta 10 ppl arn't gonna use your models with your backgrounds! Your model is the star of the show so render on a plain white BG with plenty of lighting. Rendering is an art in itself!
2) Model rating is nothing to do with the quality of the model its to do with files, formats and renders you've uploaded.
3) For your textures and low-poly workflow I suggest you learn Substance Painter or similiar package and use a PBR workflow making your model more useable/versatile across platforms.
4)Upload free models or download ones to see how others work. This will help you evaluate and develop your own skills.
5) Practise, Practise, Practise..........don't rest on your laurels and keep moving forward. Watch tutorials, the internet is a wash with some great ppl sharing their skills and knowledge. The 10,000 hr rule.......heard of it! It take that amount of time to become competent at something.

It took me 4 days to sale one of my models. But it's also the best I have on my page. I guess the quality must be good and the price must be affordable.

depending to the model