If the 2nd column is hidden and you have fixedColumnsLeft: 3 the hidden column should be fixed.
In 8.0.0-beta.2-rev3 3 visible are fixed - https://jsfiddle.net/6fk2dLn0/.

Before that, the hidden one was also fixed and therefore only two visible were fixed.
Here is a 8.0.0-beta.1 demo - https://jsfiddle.net/mp3tv6qu/

And here is a 7.4.2 demo - https://jsfiddle.net/tcf7u5p9/

@pnowak found a problem at the revision 4 that there is no displayed fixed column for option fixedColumnsLeft set to 1: https://jsfiddle.net/34uh2ndc/11.
It should be fixed within https://github.com/handsontable/handsontable/commit/cd426248931ac3dbbd31e244d56541a109cafeb1.
@AMBudnik found a problem at the revision 4 that there is thrown error while we show hidden, fixed column.
Uncaught Error: TD or TH was expected to be rendered but is not
It should be fixed within https://github.com/handsontable/handsontable/commit/fbbec5565d0eb06edfc59e42f83f3bcdae93fc74, https://github.com/handsontable/handsontable/commit/bedeadf1aea3c1d69da54effb8d14bdbde663564.
It seems that refreshSelections function of the Table element (overlays; especially LeftOverlayTable) has performed before rendering already showed columns (using start function from the view.js).
Thus, this part of the code has been performed too early.
Note: It seems that the problem has occurred only when the horizontal scroll for the table has existed.
hidden columns are not frozen solved in 8.0.0.-beta2-rev5
https://jsfiddle.net/8nrLv5b6/
fixing a single column by fixedColumnsLeft set to 1 solved in 8.0.0.-beta2-rev5
https://jsfiddle.net/cogxzh8j/
Trowing Uncaught Error: TD or TH was expected to be rendered but is not in the console solved in 8.0.0.-beta2-rev5
https://jsfiddle.net/cogxzh8j/
@wszymanski good work!
Most helpful comment
Main case
hidden columns are not frozen solved in 8.0.0.-beta2-rev5
https://jsfiddle.net/8nrLv5b6/
Case 2
fixing a single column by
fixedColumnsLeftset to1solved in 8.0.0.-beta2-rev5https://jsfiddle.net/cogxzh8j/
Error case
Trowing
Uncaught Error: TD or TH was expected to be rendered but is notin the console solved in 8.0.0.-beta2-rev5https://jsfiddle.net/cogxzh8j/
@wszymanski good work!