When Tableau reads the Excel file, it thinks there is data out in some very high number column. Hard to believe that converting the file to CSV didn't fix the problem, unless the CSV also had more than the 12 columns.
There are several possible solutions:
1. Hide the extra columns.
2. Use the "Data Interpreter" feature in Tableau. It can probably figure out the problem and skip the extra columns.
3. Go into Excel and delete all columns past the end of your data. The "Go to Special" dialog also has a choice for "Last Cell" that you might find useful. Resave the file. Reconnect in Tableau.
I deleted all columns and rows outside of my data. I know that sometimes a space can goof up the mix out there in ZZ land.
I still don't know what went wrong but I believe it is with the 2018.2 version.
I relaunched 2018.1 and opened the workbook and no problems existed.
I do not want to change to using the data interpreter because I have over 600 workbooks that I have built.
I believe this is a possible version problem. I was able to reconnect to the CSV saved version and my data-flowed perfectly in 2018.1 version.
2018.2 It didn't work. I don't recall when I upgraded from 2018.1 to 2018.2. I wonder if I got some partial install hick-up or something. I have noticed
that connect to my data is very slow each time.
Our main public server is 10.2 and to be upgraded soon so, I can't use an extract. I wish we had a choice in extract types as for now, we aren't able to uploaded the hyper extracts.
If it's a 2018.1 vs. 2018.2 issue, then I would contact support. Or you can email me the file and I'll have a look.