Porduct characteristics fail to appear

It's not a bug. It's just that it's not possible to have so many variants per products as the system needs to load them all on the same page. The design of that feature is not made for handling that. Above a few hundred of variants, normal servers cannot handle the load.

In your case you should rather use options (at least for some of your characteristics): www.hikashop.com/support/documentation/i...ct-form.html#options

Unlike characteristics, options do not combine together.
That has the drawback of not being able to refresh the product information on the fly based on the selection of options (only the price is recalculated).
For example, with characteristics, you could set a different image for each variant and have the image refresh automatically on the product page based on the choice of the user.
But it has the advantage of being able to handle much more possibilities if you use options. The same limitation apply: above a few hundreds of possibilities normal servers won't be able to handle. The difference is that instead of having 20*20*12*3 possibilities, you will have 20+20+12+3 possibilities if you only use options. So you have quite some space to add more options where with characteristics you're already way over the limitation of your server

Options are only a feature available since 1.5.0 and in our commercial versions. You will find the "options" zone between the prices and the characteristics zone, when editing/creating your products.