Its just on one table. Rebooting did nothing.
I did select the table.
Not sure what a screenshot would show. When I click on the column and the pulldown menu, I can select sort ascending or sort descending. But "add column before" and "add column after" are not selectable -- I cannot select either one (it is faint grey and not clickable). I do not have this problem on any other table or spreadsheet and cannot figure out what is different.
I only have about 20 columns that I am using and need to add in the data to the 5th column as opposed to the 21st (I can do it there and/or add new columns at the end (all the way to the right), but not in between columns
In Numbers, you have a limited number of Header columns. Once you have 5 Header Columns, and if your selected column or cell involves one of those 5 Header Columns, you are done adding Header Columns and the menu item will be grayed out. A Screen Shot would have shown Wayne which column had the focus on it.
Header Columns and Rows and Footer Rows are treated specially and have special features in Numbers. You can read about them in the Numbers User Guide, downloadable from the Help Menu.
See Using Table Tools, beginning on page 48.
I have another table in the spreadhsheet that has 18 columns and I can add a column before/after any column so I don't understand why this other table with 20 columns doesn't let me do it.
I have not added any header columns to the table in question or the other table i referenced.
If a screen shot would help, i can do it but i don't know how i can to show the greyed out add column before and after.
Here's a quick way out of the situation:
Select cell F1
Type Option-LeftArrow 5 times, creating 5 blank (Body) Columns to the left of your present Column F.
Select all the cells in columns A-E
Command-C to Copy them
Select the blank cell F1
Command-V to Paste (You now have two copies of the first five columns)
Delete (Header) Columns A-E
This process replaces your unintended 5 Header columns with Body columns and your problems with adding columns should be over.
When you get some time, read the User Guide reference on Header and Footer columns in tables.