Hey there, seems like you've already tried many solutions.
May I suggest checking if the SD card has been formatted before its first use (check to see if your SD card is formatted as a FAT16 or FAT32 partition). I have attached a link with further details on doing this.
Also make sure your SD card is not in write-protected mode (the Lock switch on your SD card should be in the off position) and try again.
As well, make sure you have the most updated software on your device.
If nothing else works, I got the below text from the Vtech website.
"If you have a problem that cannot be solved by using this manual, we encourage you to visit us online or contact our Consumer Services Department with any problems and/or suggestions that you might have. A support representative will be happy to assist you. Before requesting support, please be ready to provide or include the information below:
• The name of your product or model number (the model number is typically located on the back or bottom of your product). • The actual problem you are experiencing.
• The actions you took right before the problem occurred.
Internet : www.vtechkids.com
Phone : 1-800-521-2010 in the U.S. or 1-877-352-8697 in Canada"