OOW (out of warranty) repair is costing more than half the replacement cost and a 50 inch runs about $199.99 at https://www.walmart.com/ip/Sceptre-50-Class-FHD-1080P-LED-TV-X505BV-FSR/631796609
So try factory resetting the TV and hope that's it.
Magnavox LED HD TV Model # 46ME313VF7. Neither the Cox remote or the TV remote will turn on the TV. All other functions work. TV is 5 yrs old. Problem just started.