If your device is rooted and flashed with something that doesn't quite work, and you can't otherwise make it do what you want, it may help to "factory reset" it by flashing it with the original Samsung firmware. I'm not sure if you can get that from Samsung, but lots of sites claims to have it:
https://www.qwant.com/?q=samsung+firmware
Here is one such site, which also has a procedure for how to go about it:
https://samfw.com/firmware/GT-P7510/ROM
It's old stuff and the link they have to the Odin tool is gone, but I think this is it:
https://www.ydfile.com/file/odin/Odin3_v3.14.4.html
If it doesn't kill your device, it might get it working again