CSV Import of Matrix Items > Invalid matrixoptioncustitem reference key

Solution:
The error is encountered when a matrix option included in the CSV file is not listed or different from the Item Fields setup.

To check:

1. In the CSV Response file, take note of the ID of the matrix option that threw an error (e.g. custitem1).

2. Navigate to Customization > Lists, Records & Fields >  Item Fields.

3. Look for the ID of the matrix option indicated in the CSV Response file (e.g. custitem1).

4. In the List column, take note of the name of the list the Item Field is referring to.

5. Navigate to Customization > Lists, Records & Fields > Lists.

6. Click the name of the list referred to in number 4.

7. Under the Values tab, check if the option selected in the CSV file is listed. Values should also be spelled as how they are spelled in NetSuite. Check also if there are any unnecessary characters or spaces. Values may be case sensitive.