I have Joomla! 2.5.27. I was running 2.6.10. and just tried upgrading to 2.6.12.2 to fix this problem.
I'm not sure what triggered this, but when I choose to edit an item in the back-end, and view Custom Fields, all my Cart Variants now display the "Select an Option" popup where the field Value used to show. All the other fields, including the Price, all display correctly. (see attachment image)
On the front-end and in the database, the Values appear and work correctly.
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I installed VM3.0.0 on a test copy of my website, and it seems to have fixed the above problem; however, my VM template isn't yet compatible with VM3, so the upgrade won't be an easy solution.
It would be nice to fix this problem in VM 2.6.x.
I have maybe an idea, if you post also the config of the custom itself (administrator/index.php?option=com_virtuemart&view=custom)
Thank you in advance.
I think I've attached what you've requested.
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I mean the config if you edit it.
Attached.
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FYI, I updated to VirtueMart 2.6.14, which had no effect on this problem.
You use is a list. if you use is a list, then you must enter the list in the defaults