Avast and MSE, can not be together.

turn off your PC.

turn off all computers,
then unplug the power cable from the router,
then unplug the power cable from the (Cable) modem

…let it OFF for about 5 minutes.

Then with the computers still off,
plug back in the Cable modem power cable.

…when all the lights come on:
then plug in the router,

when all the lights come back on:
then start all computers:

Now check if your problem still exists.
Post results here!