In this scenario, you've maybe done some manipulation of your items via CSV but were editing in Microsoft Excel before importing back into Sku Grid. Microsoft Excel tends to mess up your ebay item numbers. So if you notice that under the reprice sku column, instead of your item numbers looking normal, they appear in Scientific Notation (like this 2.72526E+11) Sku Grid cannot read that and because of it, it cannot access your ebay listings. For this reason, it is recommended not to use Excel but use either Libre Office or Google Sheets (both of which are free options that will not automatically convert your numbers into scientific notation). If you insist on using Excel, then you will need to highlight the reprice_sku column and right click then change the format to Number with 0 decimal places. Save it and not open it again. Opening it again, even if just to view it, will cause Excel to ruin your numbers again.
It is recommended that you do the following to correct this.
1. Export Your Current CSV from Sku Grid -- https://www.youtube.com/watch?v=mRCkTcIyY5w
2. Correct Your eBay Item Numbers in the Reprice Sku Column (see message above about which software to use or how to fix it within Excel)
3. Save file.
4. Purge All of Your Items out of Sku Grid - https://www.youtube.com/watch?v=9H8GjnNeMqs
5. Import Revised CSV Back Into Sku Grid - https://www.youtube.com/watch?v=ss8ih7rVr1k
6. Force Reprice All Items - https://www.youtube.com/watch?v=1zK5V3D_XGg