Your required response, either   prove you have insurance coverage    proof that you sold the vehicle
What do I do if I have insurance coverage?
do not
What should I do if there is a problem?
If there is a problem, it is your responsibility to resolve it.
And what should I do with the plates while the problem is not resolved?
save the plates while solving a problem with your insurance company
I received a letter stating that my license is suspended. What I can do?
The letter means that your insurance company notified DMV that your insurance coverage ended, and that no other company notified DMV of new coverage.
What should I do if I have insurance?