Zeki TBDG773B Doesn't Recognize External SD card
The error is most likely the card is in not supported format or it is a not supported size (such as some phones only support 32 GB SD cards).

(Windows Version)The way to check the format is to plug it in to a computer then go to File Explorer &gt; Right click on the sd card &gt; Properties Then look at the file system. If the card file system is not NTFS then you have to format it. Go to File Explorer &gt; right click on the sd card &gt; Format on the format screen select file system to NTFS. NOTE:all data on sd card will delete. Leave all setting default except for ntfs format. Then click format.

Plug it into your device and it should mount and work properly. If any thing is unclear just comment.