During SSRS report for Dynamics Ax 2012, I found that when report goes on multiple pages, column header did not appear all page except the first one.
I fix this problem by setting some properties to true.
Select the tablix and below right side of columns group header and click there on small arrow head and select the advance Mode.
This will open the row group header and column groups like below picture.
Now right click on top static in row groups, or Press F4 to open the properties window.
From property window, set propertyRepeatOnNewPage to True. Also set KeepWithGroup property to After
. When you deploy the report. Column header will appear on each page.