How to verify and fix

First, perform an accessibility check, Go to Tools > Accessibility > Full Check
Then verify your table in under Tools > Accessibility > Reading Order > Select the table > click on Table Editor

Screenshots

The image below shows that you must perform an accessibility check at first and locate where the table error may reside.

The image below shows the reading order tool used to select the table. Once you have selected your table, click on "Table Editor" option.

Once you select the table editor option, the table below will highlighted. The image below is an example of a table that contains no accessibility settings.

Notice that there are no "TH" elements in the table below. This means that there are no headers present in the table and that screen readers and other assistive technologies will not be able to read through the table as it intended/visual display.

The image below shows you an example of an accessible table where we have "TH" as well as "TD" elements to structurally represent the table logically, unlike the previous example of a table.

The image below shows you how to change a incorrectly tagged table cell to a table header.

Table with Sub-Headers

The image below is an example of a complex table which contains incorrectly tagged "TH". Notice that in row 2, "Sub Header 1" is tagged as TH along with 2 empty cells.

This is common when you convert the table from an authoring application, in this case Microsoft Word to PDF. Not all the merged or customized cells will necessarily be tagged correctly.

To fix this, Go to table cell properties dialog box and modify the options accordingly. In this case, "Header 1" and "Header 2" have 2 spans of rows merged respectively.

Hence, we select the headers and change it's row span value from 1 to 2.

A warning message will always be displayed when you change the span attribute and it can result in a malformed table. Click yes if the customization is appropriate.

The image below is an example of a accessible table with all the headers tagged correctly.

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