Can someone help me update google play services?

[Android Central Question]

I recently got this smartab and all the apps I need keep telling me I can't use them until I update Google play services. I would go to the playstore, find Google services, attempt to update it and then when its almost done and installing it says "'Google Play Services' can't be installed. Try again, and if the problem continues, get help troubleshooting (its a link but I'm unable to press it). (Error code: -504)" I cleared play store data, Google play services data, and I even reset the whole tablet and I still can't do anything. Please help. Thank you.