Tables styles not applied

I defined a simple style for tables in TC CK (background color and a little more).
Then I created a simple table using the Joomla editor within an article, but the styles of TC CK haven't been applied to the table. No one of them.
What went wrong?

Hi
can you please give me the url of the page ?
CEd

Check this . Please, check the little table in the Prezzi dei corsi chapter. The larger table has been build within a Page Builder CK module.
The attached image show the table options in TC CK. As you can see, the background color and the border have not been applied.

Also note that I have added these rules to custom.css to style my tables (until TC CK works):

table {
border-spacing: 5px;
border-collapse: separate;
}

table td, table th {
padding: 10px;
}

Sorry! The little table as well is within the Page Builder module. Can be this the problem?

I copied the text of the little table directly into the article. No styling.

please switch the "table style" option to "simple" and tell me if it works

Done. It works.
I'm gonna run some tests, since not all is clear in my mind. I will let you know.
Thank you.