I just bought this tablet from Walmart on the 3rd. The return key fell off now the keyboard don't work. What can I do?

Edited question for clarity. Your tablet on made by ONN, not 'on'. Added a few commas and periods and added 'please' at the end.

The ONN 10.1 tablet is a standalone unit, so it you are using a keyboard with it, I am guessing you have this one?

https://www.walmart.com/ip/Onn-10-1-Android-Tablet-with-Detachable-Keyboard-16GB-Bonus-20-off-Walmart-eBooks-Included/400925756

This is the manual and mentions nothing regarding how to turn the keyboard on, as though it does it by magic!

https://fccid.io/2AE2WT1016M/User-Manual/User-Manual-4178532.pdf

My guess is that opening the tablet up operates a switch in the hinge like it does on a notepad computer. ONN is Walmart's own bargain basement brand electronics line made at the cheapest possible price point in China. Take it back to Walmart and ask them to show you, as it appears to be broken.

Or watch some of the review and set up videos

https://www.google.com/search?q=walmart+onn+tablet+turn+keyboard+on

..

If i were you I would take it back to Walmart and see what they say But I am afraid you can not return anything without a receipt.

If this is under a year you can return it and get a new one or have it fixed. If it is over warranty I am afraid this is one tablet that is disposable and not fixable cheap enough.

Sounds like a return to manufacturer for these. All fixable but you should not have to at all deal with this just a few months old.

If it's still on warranty, return it to the shop where you bought it for service.
Maybe it's just the battery? Get it checked but if not on warranty, I'm afraid that to repair it might cost you more then it's value. You can buy this tablet for about 50$ so you should ask how much might cost to repair it.

Normally you would have better luck returning it to WalMart than the manufacturer. You'll need the receipt. Here is a link to Walmart's return page Search

I bought my son the 7 inch RCA tablet form Walmart on Black Friday 2014. This tablet has a one year manufacturers warranty so you should still be fine with your 10.1 in tablet if you contact RCA directly.

unplug the keyboard, power cycle the tablet, and then plug it back in after booting.

If you need further help, reach me via phone at https://www.6ya.com/expert/joel_63c670a84e9f6a97

Have you tried contacting the manufacturer's customer service? You really don't want to try taking the casing apart, unless you're experienced, you might never get it back together. If it was me, if it's just a month old, you should hurry and take it and the packaging and receipt back to walmart. Tell them you either want a new one or your money back. Immediately. Here's what their web page says about their return policy

"Returns Policy by Department Most items can be returned within 90 days of when you receive them. Items purchased on Walmart.com may be returned either to a store or by mail, unless stated otherwise in the list of exceptions below. See the departments below to find out if there are exceptions to the 90-day rule and for instructions on how to return certain types of items.
Items must be returned in the original manufacturer's packaging, so we recommend you keep your packaging for at least the first 90 days after purchase."
Good luck and be assertive.

push it back in