This problem I fixed when i installation ubuntu for first time, but with the new actualization this week the problem comeback and i cant solved. Please anybody help me. Thank.
I found the solution!! here:
I’m glad you found the answer, but this site is for the co-ordination of the Ubuntu project(s), and not support.
For Ubuntu Support options, there are many listed at https://community.ubuntu.com/t/finding-help/712 (which includes Ask Ubuntu where you found your answer)