BB Table code does not render as a Table when posted. However, if you use the Table Icon in the post editor, you do see an actual table in which to enter the table data. But then when saved all you see in the BB Table code itself.
This could be a myriad of things really. Could be an outdated style. Could be a conflicting custom BB code. Could be an add-on that added tables as well.
Beyond that we'd need some specifics, such as reproducible steps for us to attempt to replicate the problem, or a URL which demonstrates the problem, or a screenshot/video etc.
This is a fresh install of 2.1.0 (yesterday). I click on the Table icon, set the dimensions, enter the table info into the table template, hit save. What I see is the [ table ] [ TR ] [ TD] a [/TD] ... BB code, not a rendered table. (I've added spaces in my example BB code so it it won't try to render it as a table.)