You did not mention what size or type of SD cards you have tried. Also did your tablet attempt to recognize any of the SD cards you tried by popping up a notification when you inserted the card? Just in case you're not aware, you do need to make sure the SD card is no larger than 32GB in storage capacity and is a microSD or microSDHC card. Here is a link to a spec sheet: https://www.cnet.com/products/rca-7-voyager-ii-tablet-android-5-0-lollipop-8-gb-7/specs/
I also have linked a page that can help you with setting up your SD card which has some useful information: https://support.google.com/android-one/answer/6088895?hl=en