Make sure that the chart you are importing from is indeed a table chart, and that both table columns have identical attributes or metrics.
These are the conditions for importing a color scheme in a chart table column.
Missing colors in column cells can be caused by the value ranges in the column color scheme. If the value ranges do not (completely) cover the values in the column, (part of) the cells in the column will not be colored.
To solve this, change the column color scheme value ranges in order to make them cover the column values.
If you switch the line chart display to stacked lines and the above message is shown, it means that one or more list values of the objects in your chart has a negative value and/or the objects do not all have the same number of list values.
An example of a "problematic" line chart is shown below.
As can be seen, Object A has three values (along the x-axis) instead of four, like the other objects. Additionally, Object C has one value that is below zero. Therefore, displaying stacked lines is not possible.
In the following chart all list values are positive, and the number of list values is the same for each object. Stacked lines can be displayed: