Maybe it is time for you to install a new build?
By the way, you might need to check root access using other app instead of Tiback up.
I use tiback-up in my other device and it does not work. I flash SuperSu and then it finally worked again.
Maybe you phone still has root access but just tibackup won't regcognize it. check root access first. Then try flash SuperSu.
You last choice is clean reinstall a new build