ShipScript has been an eBay Community volunteer since 2003, specializing in HTML, CSS, Scripts, Photos, Active Content, Technical Solutions, and online Seller Tools.
If your descriptions are plain text and do not contain embedded photos, then you don't need to use eBay's mobile checker.
If your plain text description contains an embedded photo, then eBay's mobile checker can add style code to make that image mobile friendly.
If your description contains formatting from a webpage editor, then nothing eBay can do will make your description mobile friendly. If you use eBay's tool, it will say it has fixed it by adding some tags, but when you recheck, it will still fail. Additionally, if that process adds the mobile viewport tag, your description will be even LESS friendly on a mobile device because the viewport tag tells the phone device to NOT shrink to fit, so scrollbars will be added instead.
I ran your listings through this bulk Mobile Size checker.
https://www.isdntek.com/ebaytools/MobileSizeChecker.htm
Fifteen of the listings that were already ok have the viewport set, which is fine. You have only one listing (362959384820) with an embedded image, and that is the only listing where the image style tag has been added (the viewport was not added, and it won't matter whether or not it is added because I think eBay will automatically add the viewport as the page loads for the visitor). That one description was fixed by eBays image style tag, so that is the one listing where eBay's tool was helpful.
The tool found that 17 of your listings are not mobile friendly and have not had eBay's checker applied either. eBay's checker would not have been able to help these:
254580615805
254580615941
254580616701
254580898484
254580911557
254582086032
254582111236
254582395510
254582416049
254584002255
254590340298
254591522239
362980250588
362982970284
362984865161
362988922861
362988945134
I looked more closely at item 254582086032 and see that it has a structure to create two columns, which includes a hardcoded width of width: 748.344px; which won't shrink down to the 320 width of a phone. eBay can't fix this. You'll have to fix your layout instead. I checked a few of the 17 items and they have a similar formatting issue.
An easy way to fix those is to take each of the above item numbers and run them through this tool to remove the hardcoded formatting:
https://www.isdntek.com/ebaytools/MobileSummaryEditor.htm
Paste the item number in the top slot and load the item code. Then click the button below the code display that has the three leaves. That button will strip off most code, but will leave some basic formatting in place. Copy the results and paste into your listing to replace what is currently there. Then use eBay's tools if you need to further style your text.
