Mini VGA third party not function after upgrade to new os ver 11.2.6

Third party accessories that are not MFi certified can fail at any time, and are not supported by Apple. There is no guarantee that any such accessory will work with an Apple device, and Apple only recommends that genuine Apple accessories, or those that are MFi certified be used. Updates to iOS can render any of these non-certified accessories disabled at any time. You need to replace the accessory.

If you're using a third party device to get VGA output from an iPad contact the manufacturer of that device to find out what the problem is with compatibility. Also letting us here know the name of the device and the manufacturer might help you find someone who knows more about that device.