How to import Timestamp from a CSV file
You get NULL values probably because MySQL cannot determine automatically that first column in you CSV is a timestamp.
You could try to change table structure so first column becomes a VARCHAR, then import data, then transform dates using mysql date functions (change date to mysql standard format 'Y-M-D H:i:s'), then convert back this column to timestamp.

Alternatively, you could use LOAD DATA INFILE to insert CSV data directly, but for first column use SET directive in LOAD DATA INFILE to change first column data to MySQL standard format. Example:

LOAD DATA INFILE youfile.csv 
  INTO TABLE yourtable
  FIELDS TERMINATED BY ","
  LINES TERMINATED BY "\n"
  (@var1, col_name_2, ...) SET col_name_1 = STR_TO_DATE(@var1,'%m/%d/%Y %k:%i');


This converts date to MySQL format while importing data.